Introduction

Testosterone therapy is a treatment that helps people with low levels of testosterone. Testosterone is a hormone that plays an important role in the body, especially for men. It affects muscle mass, bone strength, red blood cell production, mood, and sex drive. As men age, their testosterone levels naturally go down. Some people also have medical conditions that cause their testosterone to be lower than normal. When this happens, doctors may prescribe testosterone therapy to bring hormone levels back to normal.

In recent years, more people have started using testosterone therapy. This increase is partly due to greater awareness of low testosterone and the development of more ways to take the hormone. Some people take it as a gel, injection, patch, or even a tablet placed under the skin. The rise in use has also been influenced by advertisements and public interest in anti-aging and wellness treatments. While testosterone therapy can help people who truly need it, it has also raised questions about safety.

One of the main concerns with testosterone therapy is the risk of blood clots. A pulmonary embolism, or PE, is a serious condition where a blood clot travels to the lungs and blocks blood flow. It can cause chest pain, trouble breathing, low oxygen levels, and in some cases, death. Pulmonary embolism is often caused by a blood clot that forms in the deep veins of the legs or pelvis, a condition called deep vein thrombosis (DVT). When part of that clot breaks off and moves to the lungs, it becomes a PE.

Doctors and researchers have started to look at whether testosterone therapy might raise the risk of developing blood clots like PE. Some reports and studies have found that people taking testosterone therapy may be more likely to develop clots. However, not all studies agree. Some research has found no link between testosterone therapy and blood clots. Because of these mixed results, there is still uncertainty about how risky testosterone therapy might be in this regard.

One possible reason for a higher risk of blood clots is that testosterone therapy can increase the number of red blood cells in the body. This condition, called polycythemia, makes the blood thicker. When blood becomes too thick, it flows more slowly and can increase the chance of clotting. Other effects of testosterone on the blood and blood vessels may also play a role.

Pulmonary embolism is a life-threatening condition that needs quick treatment. Because testosterone therapy is becoming more common, and because PE is so dangerous, it is important to understand if there is a real connection between the two. People considering testosterone therapy, along with their doctors, need clear answers about the risks and benefits.

This article looks closely at the scientific research on testosterone therapy and pulmonary embolism. It reviews what testosterone therapy is, why it is used, and how it might affect the body’s ability to form blood clots. It also explains what pulmonary embolism is, how it happens, and why it is a concern for people taking hormone treatments. Research studies that have tried to answer this question will be explored, including those that support and those that question the link between testosterone and PE.

Understanding the full picture helps doctors make better decisions when starting or continuing testosterone therapy. It also helps patients know what to expect and what to watch out for. With more clear and simple information, people can make safer choices about their health. The goal is to provide accurate, easy-to-understand facts about testosterone therapy and its possible connection to pulmonary embolism based on what the research says.

What Is Testosterone Therapy and Why Is It Prescribed?

Testosterone is a hormone that plays a key role in the development and health of the male body. It helps control muscle mass, bone strength, fat distribution, red blood cell production, and sexual health. Although women also produce testosterone in smaller amounts, it is best known as the main male sex hormone.

Testosterone therapy is a medical treatment that helps raise testosterone levels in people who do not make enough on their own. This condition is called hypogonadism. When the body does not produce enough testosterone, symptoms can include low energy, reduced muscle strength, low sex drive, depression, weight gain, and trouble concentrating. Some people may also notice problems with erections, body hair loss, or breast swelling.

Doctors may prescribe testosterone therapy when blood tests show low testosterone levels and a person has symptoms linked to that shortage. Treatment is meant to bring hormone levels back to normal and reduce symptoms. However, therapy is not usually started based on symptoms alone. A clear medical diagnosis is needed to make sure the person is a good candidate for treatment.

Medical Uses for Testosterone Therapy

The main reason doctors prescribe testosterone therapy is to treat primary or secondary hypogonadism. This can happen for many reasons, such as damage to the testicles, problems with the pituitary gland, genetic conditions like Klinefelter syndrome, or certain cancers and treatments like chemotherapy. In some cases, the cause is unknown.

In teens with delayed puberty, testosterone may be used for a short time to start normal male development. In people with HIV or AIDS, testosterone therapy may also be used to help reduce weight loss and muscle wasting. Rarely, it may be used for women with certain types of breast cancer or other hormone-related conditions, but this is not common.

Ways to Take Testosterone Therapy

There are several forms of testosterone therapy, and the best type depends on a person’s needs, medical history, and lifestyle. Each type has different pros and cons.

• Injections: These are given into the muscle every 1 to 4 weeks. They are often the least expensive form but can cause ups and downs in hormone levels.

• Gels and Creams: These are applied to the skin once daily, usually on the shoulders or arms. They give steady hormone levels but require daily use and care to avoid skin contact with others.

• Patches: These are placed on the skin and changed daily. Some people may get a skin rash where the patch is applied.

• Pellets: These are small tablets placed under the skin by a doctor. They slowly release testosterone for 3 to 6 months. This form is low-maintenance but requires a minor surgical procedure.

• Oral and Buccal Tablets: These are taken by mouth or placed in the cheek. Oral tablets can affect the liver, so they are not commonly used. Buccal tablets stick to the gum and release the hormone gradually.

• Nasal Gel: This newer form is sprayed into the nose several times a day and may be better for people who cannot use skin-based products.

Increase in Testosterone Therapy Use

Over the last two decades, more people have started using testosterone therapy, especially older men. This rise is partly due to more awareness of low testosterone and marketing that links testosterone to youth and vitality. Some clinics promote therapy for symptoms like tiredness, weight gain, or mood changes, even when testosterone levels are not clearly low. This has led to concerns about overuse and safety.

Experts agree that testosterone therapy should only be used when there is a clear medical reason. Treating normal aging or using testosterone to boost athletic performance is not approved. In fact, taking testosterone without a proper medical need may cause more harm than good.

Understanding how testosterone therapy works and why it is prescribed is important before starting treatment. The goal is to use it safely and only when it can truly help a diagnosed condition.

Understanding Pulmonary Embolism: Causes, Symptoms, and Risk Factors

A pulmonary embolism (PE) is a serious medical condition that happens when a blood clot travels to the lungs and blocks one or more blood vessels. This blockage can make it hard for oxygen to move through the body and may damage the lungs or other organs. A PE can be life-threatening if not treated quickly.

Most blood clots that cause PE begin in the deep veins of the legs, a condition called deep vein thrombosis (DVT). These clots can break off and move through the bloodstream to the lungs. When a clot reaches the lungs, it gets stuck in a pulmonary artery, which is a blood vessel that carries blood from the heart to the lungs. This causes the flow of blood to stop in part of the lung.

Causes of Pulmonary Embolism

PE almost always begins with a blood clot that forms in the deep veins of the legs, thighs, or pelvis. This type of clot is called a venous thromboembolism (VTE). Clots can form when blood flow slows down, when blood becomes thicker or stickier than normal, or when the walls of blood vessels are damaged. Some common causes include:

• Long periods of immobility: Sitting for a long time during travel, bed rest after surgery, or being hospitalized for a medical condition can reduce blood flow in the legs and increase the risk of clotting.

• Surgery or injury: Major surgeries, especially those on the hips, knees, or abdomen, can increase the chance of clot formation. Injuries to blood vessels may also trigger clotting.

• Cancer: Some cancers and cancer treatments increase the risk of clots. Tumors may press on blood vessels, and some chemotherapy drugs affect clotting.

• Hormone therapy: Certain medications, including birth control pills and hormone replacement therapy, can raise the risk of blood clots. These medicines may change the way the blood clots or increase certain proteins that help clots form.

• Pregnancy: Blood becomes more likely to clot during pregnancy. This helps prevent too much bleeding during childbirth but can also raise the risk of PE.

• Genetic conditions: Some people are born with conditions that make their blood more likely to clot. These are called inherited thrombophilias and include Factor V Leiden or prothrombin gene mutations.

Symptoms of Pulmonary Embolism

The signs of a PE can appear suddenly and may differ from person to person. Common symptoms include:

• Shortness of breath: A sudden difficulty in breathing is the most frequent symptom. It can happen whether resting or moving.

• Chest pain: Sharp or stabbing pain in the chest, especially when breathing deeply or coughing. The pain may feel worse with activity and may not go away when resting.

• Coughing: A dry cough or coughing up blood (called hemoptysis) can occur.

• Rapid heartbeat: The heart may beat faster to try to make up for the lack of oxygen in the blood.

• Feeling lightheaded or dizzy: In some cases, a person may faint or feel weak due to reduced oxygen supply to the brain.

• Anxiety or a feeling of doom: Some people report a sense that something is very wrong, which can be a warning sign.

• Swelling or pain in the leg: If the PE came from a DVT, there might still be signs of a clot in the leg, such as redness, tenderness, or swelling in one limb.

These symptoms can be confused with other conditions such as a heart attack, pneumonia, or anxiety. This is why doctors often use special tests to confirm the diagnosis.

Risk Factors for Pulmonary Embolism

Certain factors increase the chances of having a PE. These include:

• Immobility: Long travel (such as plane or car rides), being confined to bed, or paralysis may slow blood flow.

• Surgery: Especially surgeries involving the legs, pelvis, abdomen, or brain. Recovery time increases the risk.

• Age: People over 60 have a higher risk due to slower blood flow and higher rates of chronic illness.

• Obesity: Being overweight adds pressure on the veins in the pelvis and legs, which can lead to clot formation.

• Smoking: Smoking damages blood vessels and makes blood more likely to clot.

• Chronic diseases: Conditions like heart failure, kidney disease, or inflammatory bowel disease can raise the risk of PE.

• Hormones and certain medications: Estrogen-based treatments and anabolic steroids, including testosterone, can raise clot risk.

• Previous DVT or PE: Having had a clot in the past greatly increases the risk of another event.

Recognizing the causes, symptoms, and risk factors of pulmonary embolism is essential. Early diagnosis and treatment can prevent serious complications and save lives. Doctors use tools like blood tests (D-dimer), imaging scans (CT pulmonary angiogram), and ultrasounds of the legs to confirm PE and find the source of the clot. Once diagnosed, treatment usually begins quickly with blood thinners and supportive care to reduce the risk of future clots and improve outcomes.

How Might Testosterone Therapy Affect Blood Clotting and Thrombosis Risk?

Testosterone therapy can change how the body makes blood and controls blood clotting. These changes may raise the risk of blood clots in some people. One of the most common side effects of testosterone therapy is an increase in the number of red blood cells. This condition is called erythrocytosis or polycythemia. When the body makes too many red blood cells, the blood becomes thicker. Thick blood moves more slowly through the blood vessels, especially the veins. Slow blood flow can lead to the formation of clots, which may break off and travel to the lungs, causing a pulmonary embolism (PE).

Erythrocytosis is a well-known effect of testosterone, especially when it is given by injection. Injections often lead to higher peaks of testosterone in the bloodstream. These peaks can stimulate the bone marrow to make more red blood cells. A high red blood cell count leads to a rise in hematocrit, which is the percentage of red blood cells in the blood. A hematocrit level above 54% is considered high and may increase the chance of clotting problems. When hematocrit becomes too high, doctors may reduce the testosterone dose or stop therapy for a short time.

Testosterone may also affect how the blood clots by changing certain proteins in the body. These proteins help the blood either form clots or prevent clots from forming. Some studies have shown that testosterone therapy can increase levels of clotting factors such as fibrinogen and thromboxane, which help form clots. At the same time, testosterone may lower levels of substances that prevent clots, such as plasminogen activator inhibitor-1 (PAI-1). This shift in balance can make the blood more likely to clot.

In addition to changing blood proteins, testosterone may affect the function of platelets. Platelets are small cell fragments in the blood that help stop bleeding by sticking to damaged blood vessel walls. Some research has found that testosterone may increase the “stickiness” of platelets, causing them to clump together more easily. This makes it more likely for small clots to form inside the veins, especially when other risk factors like smoking or obesity are also present.

Another possible effect of testosterone is on the lining of the blood vessels, called the endothelium. Healthy endothelium helps keep the blood flowing smoothly. It also helps prevent clots. Testosterone may cause changes in the endothelium that increase the risk of clotting. For example, it may reduce the ability of the endothelium to produce nitric oxide, a substance that relaxes blood vessels and keeps platelets from sticking. If nitric oxide is reduced, the blood vessels may narrow, and platelets may be more likely to form clots.

All of these effects—thicker blood, more active clotting proteins, stickier platelets, and changes in the blood vessel lining—may raise the risk of developing venous thromboembolism (VTE). This includes both deep vein thrombosis (DVT), which occurs in the legs or pelvis, and pulmonary embolism, which happens when a clot travels to the lungs.

It is important to note that not everyone who takes testosterone will have these problems. The effects depend on many factors, including the person’s age, dose of testosterone, how it is taken, and other health conditions. However, the possible changes in blood flow and clotting show why doctors must monitor patients closely during testosterone therapy. Regular blood tests, especially to check hematocrit and hemoglobin levels, help reduce the risk of serious problems.

Understanding how testosterone therapy can affect blood clotting makes it easier to see why some people might develop a pulmonary embolism. While this risk may be small for many patients, it is still something that doctors and patients need to think about when deciding whether to start or continue therapy.

What Does the Research Say About Testosterone Therapy and Risk of Pulmonary Embolism?

Doctors and scientists have studied testosterone therapy for many years. Some of these studies suggest that testosterone therapy may raise the risk of blood clots, including pulmonary embolism (PE), while others do not show a clear link. Pulmonary embolism happens when a blood clot travels to the lungs and blocks blood flow, which can be life-threatening. Understanding what research shows is important for making safe decisions about treatment.

Studies Showing No Clear Link

Some large studies have not found strong proof that testosterone therapy causes pulmonary embolism. For example, a 2016 study published in the Journal of the American Medical Association (JAMA) looked at men who took testosterone and compared them to men who did not. The researchers found no higher rate of blood clots or PE in men using testosterone.

Another study in 2020 used data from men in the U.S. Veterans Affairs healthcare system. It followed thousands of men over several years. The researchers found that men with low testosterone who were treated to reach normal testosterone levels did not have a higher risk of venous thromboembolism (VTE), which includes both deep vein thrombosis (DVT) and PE. In fact, some of the treated men had slightly lower rates of blood clots than untreated men.

These types of studies often use medical records and compare large groups. They are called observational studies. While they are helpful, they cannot always prove cause and effect.

Studies That Suggest a Higher Risk

Other studies do show a possible link between testosterone therapy and an increased risk of blood clots. A 2013 study in the journal BMJ found that men using testosterone had a higher chance of developing blood clots in the first few months after starting treatment. The risk seemed to be highest within the first 90 days.

In 2014, the U.S. Food and Drug Administration (FDA) reviewed reports of blood clots and warned that testosterone therapy might raise the risk of venous thromboembolism, including PE. After this, the FDA required drug companies to update the warning labels on testosterone products.

Another 2019 study published in The Lancet Diabetes & Endocrinology looked at the timing of blood clots after men started testosterone therapy. It found a slightly higher risk during the first six months, especially in men who already had clotting risk factors like obesity or a history of DVT.

Differences Between Types of Studies

It is important to understand the difference between observational studies and randomized controlled trials (RCTs). Observational studies watch what happens to people who are already taking a drug. These studies can include large numbers of people, but they are not perfect. They may miss details or mix up results because of other health problems.

On the other hand, RCTs are designed to compare groups of people randomly assigned to get a treatment or a placebo. These are more reliable for testing cause and effect. However, most RCTs on testosterone therapy have not been large enough to detect rare events like PE. Because of this, much of what is known about PE risk comes from observational studies and post-marketing reports.

What Reviews and Meta-Analyses Show

Researchers often combine data from many studies to get a clearer picture. This is called a meta-analysis. A 2016 meta-analysis published in Medicine looked at more than 30 studies and found no strong link between testosterone therapy and blood clots. However, another review in The Journal of Clinical Endocrinology & Metabolism pointed out that more studies are needed, especially for men with clotting risk factors.

Some meta-analyses say the risk is small, while others suggest caution for men who are already at risk. This shows that the medical community still has questions and that the research is ongoing.

Study Limitations and Confusion in Results

Many of the studies have limits. Some did not measure how much testosterone men received. Others did not check for other risk factors like smoking, obesity, or family history of clots. In some cases, men using testosterone were already sicker or had more health problems than those not using it. These differences can make it hard to understand the true effect of testosterone.

Also, not all studies follow people long enough to see the full risk. Pulmonary embolism is not very common, so even large studies may not find enough cases to make firm conclusions.

The research shows mixed results. Some studies suggest a small increase in PE risk after starting testosterone, especially in men with other health risks. Other studies show no added risk. More high-quality research is needed to fully understand the connection. Until then, doctors may use careful judgment when deciding whether testosterone therapy is safe for each person.

Are Certain Individuals More Susceptible to PE During Testosterone Therapy?

Not everyone has the same risk of developing a pulmonary embolism (PE) while using testosterone therapy. Some people are more likely to have blood clots because of their medical history, inherited conditions, or changes caused by the treatment itself. Understanding these risk factors helps doctors decide if testosterone therapy is safe for a patient and how closely they should be watched during treatment.

Inherited Thrombophilia: Genetic Risk for Clots

Some people are born with a higher risk of blood clots due to a group of conditions called inherited thrombophilias. These genetic conditions make the blood clot more easily than normal. The two most common inherited thrombophilias are Factor V Leiden mutation and the prothrombin G20210A gene mutation.

Factor V Leiden is the most common genetic clotting disorder in people of European descent. It makes a person’s blood resistant to a natural protein that helps stop clotting. As a result, clots form more easily and are more likely to travel to the lungs, causing a PE. People with one copy of the mutated gene have a moderate risk, while those with two copies (one from each parent) have a much higher risk.

The prothrombin gene mutation increases the level of prothrombin, a protein important for blood clotting. This makes the blood more likely to form dangerous clots. Like Factor V Leiden, having one copy of the gene raises the risk, and having two copies increases it even more.

If someone with one of these conditions starts testosterone therapy, the therapy may raise their clotting risk even higher. Testosterone can increase the number of red blood cells, thicken the blood, and affect the lining of blood vessels. These changes can combine with the genetic condition to create a greater chance of developing deep vein thrombosis (DVT) or a pulmonary embolism.

Doctors may order blood tests to check for these genetic factors, especially if a person has a family history of blood clots. Knowing this information ahead of time helps prevent serious problems during therapy.

History of DVT or PE

People who have had a deep vein thrombosis or a pulmonary embolism in the past have a higher chance of having another one. These conditions can happen again, especially if the cause of the first clot is still present or unknown.

Testosterone therapy can add to this risk because it changes blood thickness and may affect how blood flows through the veins. For someone with a history of clots, these changes can make another clot more likely. Because of this, doctors often avoid prescribing testosterone therapy to people with a past history of DVT or PE unless the treatment is absolutely necessary. If it must be used, close monitoring and possible blood thinning treatment may be required.

Polycythemia: A Side Effect of Testosterone

Testosterone therapy can increase the body’s production of red blood cells. This condition is called polycythemia. While red blood cells are important for carrying oxygen, too many of them can make the blood thick and slow-moving. Thick blood is more likely to form clots, which can then break off and travel to the lungs, leading to a pulmonary embolism.

The risk of polycythemia is higher with injectable forms of testosterone and with higher doses. Doctors usually monitor red blood cell levels during therapy by checking hematocrit and hemoglobin through regular blood tests. If these levels become too high, the dose may be lowered or treatment may be paused to reduce the risk of clots.

Age, Obesity, and Other Medical Conditions

Older adults tend to have a higher risk of blood clots, especially if they also have other risk factors like heart disease or diabetes. Aging can cause changes in blood vessels, making it easier for clots to form. Since many older men seek testosterone therapy for age-related symptoms, this group must be carefully evaluated before starting treatment.

Obesity is another important risk factor. Extra weight puts pressure on veins in the legs, which can slow blood flow and lead to clot formation. Obesity is also linked to inflammation, which may further raise the risk of blood clots. When combined with testosterone therapy, which can raise red blood cell counts, the risk becomes even greater.

Certain medications can also add to the risk. Steroids, cancer treatments, and drugs that affect hormones may work with testosterone to increase clotting. A full review of a person’s medications is important before starting therapy.

People with genetic clotting conditions, a past history of DVT or PE, polycythemia, older age, obesity, or certain other health conditions may be more likely to develop a pulmonary embolism while on testosterone therapy. Careful screening, regular monitoring, and personal risk assessment are key to lowering this risk and using testosterone safely.

Does the Route or Dosage of Testosterone Influence PE Risk?

Testosterone therapy can be given in several different forms. The way testosterone is given and the amount used may affect how the body reacts. Some studies suggest that the route and dosage of testosterone may change the risk of developing a blood clot in the lungs, called a pulmonary embolism (PE). Understanding these factors is important for making safe treatment decisions.

Different Routes of Testosterone Administration

Testosterone can be given through injections, skin patches, gels, creams, oral tablets, or pellets placed under the skin. Each method changes how testosterone enters the bloodstream and how the body processes it.

Injectable testosterone is one of the most common forms used. It is often given every one to two weeks as an intramuscular shot. After an injection, testosterone levels in the blood rise quickly and may go higher than normal. These high peaks may lead to more red blood cell production. A higher number of red blood cells can make the blood thicker, which might increase the risk of blood clots. Some studies have shown that people using injectable testosterone are more likely to have high hematocrit levels, a sign that the blood has become too thick. This condition is called erythrocytosis and is linked to a higher risk of developing a blood clot, including PE.

Transdermal testosterone, such as patches, gels, or creams, delivers the hormone through the skin. These forms release testosterone more slowly and steadily. Because they avoid sudden peaks in hormone levels, they may carry a lower risk of causing the blood to thicken. Some research suggests that people using skin-based testosterone therapy are less likely to have major changes in blood thickness or clotting factors compared to those using injections.

Testosterone pellets are small implants placed under the skin, usually in the hip area. These pellets release testosterone slowly over several months. While this method avoids frequent hormone swings, it can still lead to a gradual rise in red blood cell counts. There is less research on the long-term clotting risks of pellet use, but they may have a similar effect to other long-acting forms of testosterone.

Oral testosterone is rarely used because it can be hard on the liver. Most guidelines do not recommend this route. Some older studies linked oral testosterone to changes in clotting proteins, but due to limited use today, its connection to PE risk is not well understood.

Dosage and Its Impact on PE Risk

The amount, or dose, of testosterone also plays a role in safety. Some people are given high doses of testosterone, sometimes called supraphysiologic doses. These levels are higher than what the body would normally produce. High doses can lead to a much greater rise in red blood cell count and hemoglobin. This can make the blood thicker and slower to move through blood vessels. Slow-moving blood is more likely to form clots, which can break off and travel to the lungs, causing PE.

People using testosterone for bodybuilding or non-medical reasons may use much higher doses than prescribed for medical treatment. This kind of use has been linked to a higher risk of heart problems and blood clots, including pulmonary embolism.

In contrast, physiologic doses are designed to replace testosterone to normal levels seen in healthy people. When used in proper doses under medical supervision, the risk of blood changes is often lower. However, even normal doses can cause side effects in some individuals, especially those with other risk factors.

Duration of Therapy and Cumulative Exposure

The length of time a person uses testosterone can also affect risk. Longer use means more total exposure to the hormone. Over time, even small increases in blood thickness or clotting ability may become more significant. Some studies have found that the risk of PE is highest in the first six months of testosterone use, especially in people who already have a higher risk for blood clots.

Still, long-term use without regular checkups can allow problems to go unnoticed. Routine blood tests are often used to check for high red blood cell counts. These tests help reduce the chance of problems developing over time.

Monitoring Testosterone and Blood Parameters

Monitoring is key to keeping testosterone therapy safe. Blood levels of testosterone should be checked regularly to make sure they are not too high or too low. Hematocrit and hemoglobin levels should also be tested. If these levels rise above safe limits, the dose may need to be lowered, or therapy may need to be stopped for a time. Some doctors may also recommend donating blood to reduce red blood cell levels if they become too high.

By choosing the right form, dose, and schedule for testosterone therapy, and by checking blood levels regularly, it is possible to reduce the risk of serious side effects like pulmonary embolism. Research is still ongoing, but what is known so far shows that careful planning and follow-up are important for anyone using testosterone therapy.

What Are the Clinical Guidelines Saying About Testosterone Therapy and PE/VTE Risk?

Testosterone therapy (TT) is commonly used to treat men with low testosterone levels, a condition known as hypogonadism. As more men use testosterone treatments, doctors and health agencies have looked closely at how safe these treatments are. One concern is whether testosterone therapy increases the risk of blood clots in the lungs, also called pulmonary embolism (PE), or other types of venous thromboembolism (VTE).

Several professional medical organizations and government health agencies have issued clinical guidelines and safety warnings to help doctors safely prescribe testosterone therapy. These guidelines are based on current research and are meant to lower the risk of serious side effects, including blood clots.

Endocrine Society Guidelines

The Endocrine Society is a well-known organization that sets medical guidelines for hormone treatments. It recommends using testosterone therapy only in men who have clearly low testosterone levels confirmed by blood tests, along with symptoms such as fatigue, low libido, or depression.

Their guidelines suggest that testosterone should not be given to men who have had a recent blood clot, especially in the legs or lungs. This is because testosterone may raise the number of red blood cells in the body, which can make the blood thicker. Thicker blood can make clots more likely to form. For this reason, doctors are advised to test the patient’s blood regularly to check red blood cell levels, also called hematocrit. If hematocrit goes too high, the treatment may need to be stopped or adjusted.

The Endocrine Society also advises that doctors talk to patients about the possible risks of blood clots before starting therapy. If a man has known risk factors for blood clots—such as obesity, older age, or a family history of clotting problems—the doctor may decide not to prescribe testosterone or may monitor the patient more closely.

American Urological Association (AUA) Guidelines

The American Urological Association also gives guidance on testosterone therapy. The AUA supports the idea that testosterone should be used only when a man has both low blood levels and related symptoms. Like the Endocrine Society, the AUA recommends caution in men who may be at higher risk for VTE or PE.

The AUA does not say that testosterone therapy directly causes PE. However, it does stress the importance of regular blood tests during treatment. These tests help make sure that blood thickness and hormone levels stay within safe limits. If a patient’s red blood cell count rises too much, the doctor may lower the dose or stop treatment for a time.

The AUA also says that doctors should evaluate each patient carefully before starting therapy. A detailed health history and physical exam can help find men who might have clotting risks that make testosterone therapy unsafe.

U.S. Food and Drug Administration (FDA) Safety Communication

In 2014, the U.S. Food and Drug Administration (FDA) released a safety warning about testosterone products. The agency said that testosterone might raise the risk of heart attacks, strokes, and blood clots in the lungs. This warning came after studies showed mixed results about the safety of testosterone therapy.

The FDA required companies to update the labels of all approved testosterone products. The new labels warn about possible risks, including PE and VTE. These changes were made to inform both doctors and patients about potential side effects.

The FDA has also said that testosterone should not be used to treat the normal drop in testosterone levels that comes with aging. The agency believes that more research is needed to fully understand the risks in older men who take testosterone for reasons not clearly related to disease.

Recommendations for Risk Screening and Monitoring

All three organizations—Endocrine Society, AUA, and FDA—agree that doctors should check for risk factors before starting therapy. Some common risk factors include:

• A personal or family history of blood clots

• Known clotting disorders, such as Factor V Leiden mutation

• Smoking

• Obesity

• Use of medications that affect blood clotting

After starting therapy, patients should have regular blood tests to check testosterone levels, hematocrit, and hemoglobin. If the red blood cell count rises above 54%, the risk of clots goes up. At that point, doctors may need to pause treatment or reduce the dosage.

It is also important for patients to report any symptoms of PE, such as sudden chest pain, shortness of breath, or leg swelling. Catching these problems early can help prevent serious complications.

Medical guidelines from respected organizations urge careful patient selection and regular monitoring to lower the risks of testosterone therapy. While research is still ongoing, doctors are advised to be cautious when prescribing testosterone, especially for men with existing clotting risks. Following these guidelines can help reduce the chances of PE and other serious side effects.

How Can Clinicians Minimize Risk of Pulmonary Embolism in Patients on Testosterone Therapy?

Testosterone therapy (TT) can improve symptoms for people with low testosterone, but it may also carry risks. One of the serious risks being studied is the chance of developing blood clots in the lungs, known as pulmonary embolism (PE). To lower the risk of PE in people taking testosterone therapy, healthcare professionals follow a number of careful steps.

Baseline Thrombophilia Screening in High-Risk Patients

Some people have inherited conditions that make their blood more likely to form clots. These are called thrombophilias. Common examples include Factor V Leiden mutation, prothrombin gene mutation, protein C or protein S deficiency, and antithrombin deficiency. These conditions may not cause symptoms on their own, but they can raise the risk of deep vein thrombosis (DVT) and pulmonary embolism, especially when other risk factors like hormone therapy are added.

Before starting testosterone therapy, a doctor may check for these clotting disorders in people who have a personal or family history of blood clots. Testing can include blood tests and sometimes genetic testing. Identifying these conditions early allows for better decision-making about whether to begin testosterone therapy or to take extra precautions.

Regular Monitoring of Hematocrit, Hemoglobin, and Coagulation Panels

Testosterone therapy can raise red blood cell levels in the body. This condition is called polycythemia. When red blood cell levels go too high, the blood becomes thicker, making it harder to flow through blood vessels. This can increase the risk of blood clots.

To monitor this, healthcare providers measure hematocrit and hemoglobin levels regularly. Hematocrit is the percentage of red blood cells in the blood. If this number becomes too high—usually over 54%—the risk of clotting increases. Doctors may also check coagulation panels, which are blood tests that show how quickly the blood clots. These tests can help catch early signs of problems.

These checks are usually done every few months during the first year of therapy and then once or twice a year after that, depending on the patient’s health and response to treatment.

Dose Adjustments or Stopping Therapy When Thresholds Are Exceeded

If blood test results show high hematocrit or hemoglobin levels, the dose of testosterone may need to be reduced. Sometimes, switching to a different form of testosterone, such as a lower-dose gel or patch instead of an injection, can help keep blood levels more stable.

In cases where blood thickness stays too high even after adjusting the dose, therapy may need to be stopped for a period of time or permanently. The risks of treatment must be weighed against the benefits. In such cases, other ways to manage low testosterone symptoms might be explored.

Consideration of Anticoagulation in Select Patients

In some high-risk patients, especially those with a history of clotting or confirmed thrombophilia, blood-thinning medications may be considered. These medications, called anticoagulants, help prevent clots from forming.

Anticoagulation is not recommended for every patient on testosterone therapy because these medications also carry risks, such as bleeding. However, in people who are at very high risk for clots, including those with past episodes of PE or DVT, the benefits may outweigh the risks.

This decision is made carefully by the healthcare provider after reviewing the patient's full medical history, risk factors, and current condition.

Patient Education on the Signs of Thromboembolism

One of the most important ways to reduce the danger of pulmonary embolism is to help patients understand the warning signs. A pulmonary embolism can happen suddenly and may become life-threatening. Quick treatment saves lives.

Symptoms to watch for include:

• Sudden shortness of breath

• Sharp chest pain that may get worse with deep breaths

• Fast heartbeat

• Coughing up blood

• Feeling lightheaded or faint

If any of these symptoms appear, the person should seek emergency care right away.

Patients are also encouraged to report other signs of possible clots, such as leg pain or swelling, which can signal a deep vein thrombosis. A DVT can travel to the lungs and become a PE.

Clear communication between doctors and patients helps ensure that any problems are noticed and treated early. Written instructions, follow-up visits, and phone check-ins can help make sure the therapy remains safe.

Conclusion

Testosterone therapy has become more common in recent years. Many men use it to treat low testosterone levels, which can cause fatigue, low sex drive, and muscle loss. Some women also use testosterone for specific health issues. While testosterone therapy can help improve quality of life in people with certain conditions, concerns remain about its possible risks. One serious concern is whether testosterone therapy increases the chance of getting a pulmonary embolism.

A pulmonary embolism, or PE, is a blockage in one of the blood vessels in the lungs. It usually happens when a blood clot forms in the deep veins of the legs or pelvis, a condition called deep vein thrombosis (DVT), and then travels to the lungs. A PE can be very dangerous. It can cause chest pain, shortness of breath, or even death if not treated quickly. Because hormone therapies like birth control and estrogen are already known to increase clotting risks, doctors have looked closely at testosterone to see if it has a similar effect.

Some studies have shown that testosterone therapy may increase the number of red blood cells in the body. This condition, known as polycythemia, can make the blood thicker. Thicker blood can move more slowly through veins and may lead to clots. In turn, these clots can break off and travel to the lungs, causing a pulmonary embolism. Other studies have looked at changes in blood clotting factors or how testosterone affects the inner lining of blood vessels. These possible changes could also raise the chance of a clot forming.

Despite these concerns, research on this topic does not always agree. Some studies found a higher risk of venous thromboembolism (VTE), including PE, in people using testosterone. Other studies found no clear link. Some researchers say that early users of testosterone therapy might have a slightly higher risk during the first few months of treatment. After that, the risk seems to go down. Many of these studies had small sample sizes or included people who already had a higher risk of blood clots, such as older adults or people with obesity, cancer, or inherited blood conditions. These factors can make it harder to know if testosterone itself caused the increased risk.

Medical guidelines try to help providers manage this uncertainty. Several groups, including the Endocrine Society and the American Urological Association, have released guidance about how to use testosterone therapy safely. These recommendations say that testosterone should only be prescribed to people with proven low levels, confirmed by lab tests. They also suggest checking a patient’s risk for blood clots before starting treatment. This includes asking about personal or family history of blood clots, screening for clotting disorders in some cases, and watching for symptoms like leg swelling or sudden shortness of breath.

Doctors are also encouraged to monitor people closely during treatment. This includes regular blood tests to check red blood cell counts and hematocrit levels. If these levels get too high, the dose of testosterone may need to be lowered or stopped. In people who are found to be at high risk for clots, the provider may choose not to start therapy or may consider other treatments. For people who do receive testosterone, teaching them to recognize the signs of a possible blood clot can help prevent serious problems.

More research is still needed. Large, long-term studies that compare people who use testosterone to those who do not could help give clearer answers. These studies should also look at different types of testosterone (like injections versus gels) and different doses, since the route and amount may affect risk.

In summary, testosterone therapy may slightly increase the risk of pulmonary embolism in certain individuals, especially those who already have risk factors for blood clots. However, the current research is not strong enough to say that testosterone therapy always causes this problem. With careful screening, proper dosing, and regular check-ups, many people can use testosterone therapy safely. It is important for healthcare providers to balance the benefits and risks of this treatment, using clear clinical guidelines and patient history to guide decisions.