Jatenzo (testosterone undecanoate) is a prescription drug used to treat low testosterone levels. Jatenzo can cause side effects that range from mild to serious. Examples include headache and increased blood pressure.

Jatenzo is used in adult males* to treat low testosterone levels.

The active ingredient in Jatenzo is testosterone undecanoate. (An active ingredient is what makes a drug work.) The drug comes as a capsule that you swallow.

Keep reading to learn about the common, mild, and serious side effects Jatenzo can cause. For a general overview of the drug, including details about its uses, see this article.

* In this article, we use the term “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Some people may experience mild to serious side effects during their Jatenzo treatment. Examples of this drug’s commonly reported side effects include:

Read on to learn about other possible mild and serious side effects of Jatenzo.

* Jatenzo has a boxed warning for the risk of this side effect. This is the most serious warning from the FDA. To learn more, see the “Side effects explained” section below.

Jatenzo may cause mild side effects in some people. Examples that have been reported with this drug include:

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And do not stop taking Jatenzo unless your doctor recommends it.

Jatenzo may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

* To learn more about this side effect, see the “Side effects explained” section below.

Serious side effects can occur with Jatenzo. Some are more common, while others are rare. Serious side effects that have been reported with this drug include:

If you develop serious side effects while taking Jatenzo, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after using Jatenzo, but this side effect wasn’t reported in studies.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Jatenzo, visit MedWatch.

Get answers to some frequently asked questions about Jatenzo’s side effects.

Can Jatenzo be used for bodybuilding? If so, does taking it for this use cause different side effects?

No, Jatenzo is not approved for use in bodybuilding. It’s only approved to treat low testosterone levels in adult males.* But some people misuse anabolic steroids to help build muscle in bodybuilding. (Anabolic steroids are lab-made versions of testosterone.)

Jatenzo contains a kind of testosterone, but it’s not known what side effects it may cause if it’s taken for bodybuilding. In general, misusing high amounts of testosterone for this purpose can lead to serious side effects, including aggression, liver damage, and heart disease.

It’s important that you only take Jatenzo if your doctor has prescribed it. And you should only take it for the condition your doctor prescribed it to treat. If you have questions about using Jatenzo for other purposes, talk with your doctor.

* In this article, we use the term “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Are side effects of Jatenzo similar to those of testosterone cypionate injection?

Yes, many side effects of Jatenzo are similar to those of Depo-Testosterone (testosterone cypionate injection). But Jatenzo may cause different side effects as well.

For example, both Jatenzo and Depo-Testosterone may cause headache and nausea. And both drugs may increase blood pressure* and the risk of heart attack and stroke.

But Jatenzo may also cause burping, diarrhea, and indigestion (upset stomach). These side effects aren’t known to occur with Depo-Testosterone.

For lists of possible side effects of Jatenzo, see the sections above. To learn more about Depo-Testosterone’s side effects, talk with your doctor.

* Jatenzo has a boxed warning for the risk of this side effect. This is the most serious warning from the FDA. To learn more, see “Side effects explained” just below.

Learn more about some of the side effects Jatenzo may cause.

Risk of increased blood pressure

Jatenzo has a boxed warning for the risk of increased blood pressure. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). Increased blood pressure was a common side effect in studies of Jatenzo, but most people had only small increases in their blood pressure.

You likely won’t have symptoms of increased blood pressure unless it’s suddenly severely high (hypertensive crisis). Symptoms of a hypertensive crisis include headache and blurry vision. Hypertensive crisis is a life threatening medical emergency requiring immediate treatment in a hospital or emergency room.

In rare cases, even small increases in blood pressure may lead to heart attack or stroke. And these conditions can be fatal for some people. Your risk of heart attack or stroke with Jatenzo may be higher if you’ve had these conditions in the past. Possible symptoms of heart attack and stroke include:

  • pain in your arm, shoulder, neck, or chest
  • shortness of breath
  • trouble walking or speaking
  • weakness in your face, arm, or leg on one side of your body

What might help

Your doctor will likely check your blood pressure while you’re taking Jatenzo. They may also recommend that you check your blood pressure with a home monitor. They can show you how to use it and tell you how often to check your blood pressure.

If you have increased blood pressure with Jatenzo, your doctor can tell you whether to continue taking it. They may give you blood pressure medications to help lower your blood pressure.

If you have symptoms of severely high blood pressure with Jatenzo, tell your doctor right away. But if your symptoms seem life threatening or you’re having symptoms of heart attack or stroke, call 911 or your local emergency number immediately.

Low level of high-density lipoprotein (HDL) cholesterol

Jatenzo may lower the level of high-density lipoprotein (HDL) cholesterol in your body. This was a less common side effect in studies of the drug. HDL cholesterol is often referred to as “good” cholesterol. It helps remove other types of “bad” cholesterol from your body.

Low HDL cholesterol doesn’t usually cause symptoms. To find out whether you have low HDL, your doctor will order a blood test called a lipid panel.

What might help

Your doctor will likely check your cholesterol levels from time to time while you’re taking Jatenzo. If you’re found to have low HDL cholesterol, they can recommend ways to increase your HDL levels. For example, they may recommend eating whole grains and other high fiber foods. They may also advise you to make other lifestyle changes, such as stopping smoking and being more physically active.

High levels of red blood cells and hemoglobin

Taking Jatenzo may lead to high levels of red blood cells (RBCs) and hemoglobin (Hgb). (Hgb is a protein found in red blood cells.) This was one of the more common side effects in the drug’s studies. Symptoms of high RBCs and Hgb include:

Having high RBCs and Hgb may also increase your risk of blood clots, which could lead to heart attack or stroke.

What might help

Before you start Jatenzo, your doctor will order blood tests to check your RBC and Hgb levels. They’ll continue checking these levels every 3 months while you’re taking the drug or any time you have symptoms of high RBC and Hgb levels.

If you’re found to have high levels of RBC and Hgb, your doctor may temporarily stop your Jatenzo treatment. They may have you restart the drug once your levels return to normal. If your RBC and Hgb levels increase after restarting the drug, your doctor will likely switch you to a different treatment.

Mood changes

Jatenzo may cause mood changes, including depression and suicidal thoughts or behavior, but these changes were rare in the drug’s studies. Examples of symptoms that can occur with mood changes include:

  • feeling hopeless, worthless, sad, or angry
  • losing interest in activities you used to enjoy
  • sleeping more or less than usual
  • changes in appetite or weight
  • thoughts of death or dying

What might help

If you notice mood changes while taking Jatenzo, tell your doctor right away. They can recommend whether it’s safe to keep taking this drug. If you have thoughts of suicide or death, immediately call your doctor or the Suicide and Crisis Lifeline at 988. You can also call 911 or your local emergency number.

Allergic reaction

Like most drugs, Jatenzo can cause an allergic reaction in some people, but this side effect wasn’t reported in studies. Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin (usually in your eyelids, lips, hands, or feet)
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms. Examples include:

If your doctor confirms you’ve had a mild allergic reaction to Jatenzo, they’ll decide if you should continue taking it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Jatenzo, they may have you switch to a different treatment.

Help is out there

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.

If you are not in the same household, stay on the phone with them until help arrives.

Below are important warnings for Jatenzo.

Boxed warning: Risk of increased blood pressure

Jatenzo has a boxed warning for the risk of increased blood pressure. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). Taking Jatenzo may cause increased blood pressure. In rare cases, this may lead to a heart attack or stroke, which can be fatal. To learn more, see the “Side effects explained” section above.

Other warnings

Jatenzo may not be right for you if you have certain medical conditions. This is known as a drug-condition interaction. Other factors may also affect whether Jatenzo is a good treatment option for you. Talk with your doctor about your health history before starting this medication. Factors to consider include those described below.

Certain cancers. Before starting Jatenzo, tell your doctor if you have certain cancers, including prostate and breast cancer. Taking this drug while you have certain cancers may lead to high blood calcium levels. Your doctor can tell you whether your specific cancer has this risk. If it does, they’ll check your blood calcium levels regularly during your Jatenzo treatment.

Taking Jatenzo while you have prostate or breast cancer could worsen these cancers. Your doctor will likely suggest another treatment for your condition.

Enlarged prostate. Before taking Jatenzo, tell your doctor if you have an enlarged prostate. The drug can cause enlarged prostate as a side effect, which could worsen your condition. Your doctor can recommend whether Jatenzo is a safe treatment option for you.

Heart problems. Jatenzo may cause edema (fluid buildup in your body) in people with heart problems. If you have a heart problem, such as heart failure, talk with your doctor before starting this drug. They’ll likely watch you closely for edema symptoms during your treatment.

Kidney problems. Taking Jatenzo may lead to edema in people with kidney problems, such as kidney failure. If you have a kidney problem, tell your doctor before starting Jatenzo. They’ll watch you for symptoms of fluid buildup during your treatment.

Liver problems. Jatenzo may cause edema in people with liver problems. If you have a liver problem, such as liver failure, tell your doctor before taking Jatenzo. They’ll likely watch you closely for edema symptoms while you take this drug.

Lung problems. Before taking Jatenzo, tell your doctor if you have a lung problem. Examples include asthma and chronic obstructive pulmonary disease (COPD). Taking Jatenzo when you have a lung problem may increase your risk of sleep apnea as a side effect. Your doctor can recommend whether Jatenzo is a safe treatment option for you.

Mental health conditions. If you have a mental health condition, your doctor can recommend whether Jatenzo is safe for you. People with mental health conditions may have new or worsened depression, suicidal thoughts, anxiety, or other mood changes with this medication.

Obesity. People with obesity may have a higher risk of sleep apnea as a side effect of Jatenzo. If you have obesity, your doctor can recommend whether this treatment is a safe option for you.

Allergic reaction. If you’ve had an allergic reaction to Jatenzo or any of its ingredients, your doctor will likely not prescribe it for you. Ask them about other medications that might be better options.

Alcohol and Jatenzo

It should be safe to drink alcohol in moderation while taking Jatenzo. But keep in mind that consuming large amounts of alcohol can lead to low testosterone levels, the condition this drug is used to treat. So drinking a lot of alcohol while taking this drug can make it hard to tell if the drug is working.

If you drink alcohol, talk with your doctor about an amount (if any) that’s safe for you with Jatenzo.

Pregnancy and breastfeeding while taking Jatenzo

Jatenzo is not prescribed for use in pregnancy or while breastfeeding. The drug is only prescribed for use in adult males.* For more information about Jatenzo and pregnancy or breastfeeding, talk with your doctor.

* In this article, we use the term “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Keeping track of side effects

During your Jatenzo treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking a new drug or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Taking notes and sharing them with your doctor will help them learn more about how Jatenzo affects you. They can then use this information to adjust your treatment plan if needed.

Jatenzo is used to treat low testosterone levels. Both mild and serious side effects are possible. If you have questions about the side effects Jatenzo can cause, talk with your doctor or pharmacist. Examples to help get you started include:

  • Does my age increase my risk of any side effects from this drug?
  • Will I need any lab tests to check for side effects of Jatenzo?
  • How do Jatenzo’s side effects compare with other drugs used for low testosterone, such as Kyzatrex and Tlando?

To learn more about Jatenzo, see these articles:

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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.