Jatenzo (testosterone undecanoate) is a brand-name oral capsule prescribed for testosterone deficiency in some adults. As with other drugs, Jatenzo can cause side effects, such as headache, nausea, diarrhea, and increased blood pressure.

Jatenzo can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took Jatenzo in clinical trials:

* For more information about this side effect, see the “Side effect specifics” section below.
† Jatenzo has a boxed warning for this side effect. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Side effect specifics” section below.

Mild side effects can occur with Jatenzo treatment. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to Jatenzo’s prescribing information.

Mild side effects that have been reported with Jatenzo include:

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you develop a side effect while taking Jatenzo and want to tell the FDA about it, visit MedWatch.

* An allergic reaction is possible after using Jatenzo. However, this side effect wasn’t reported in clinical trials. To learn more, see the “Side effect specifics” section below.

Jatenzo may cause serious side effects. Although serious side effects are rare, they can occur. The list below may not include all possible serious side effects of the drug. For more information, you can refer to Jatenzo’s prescribing information.

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.

Serious side effects that have been reported and their symptoms include:

* For more information about this side effect, see the “Side effect specifics” section below.
† An allergic reaction is possible after using Jatenzo. However, this side effect wasn’t reported in clinical trials. To learn more, see the “Side effect specifics” section below.
‡ Jatenzo has a boxed warning for this side effect. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Side effect specifics” section below.

Suicide prevention

If you know someone at immediate risk of self-harm, suicide, or hurting another person:

  • Ask the tough question: “Are you considering suicide?”
  • Listen to the person without judgment.
  • Call 911 or the local emergency number, or text TALK to 741741 to communicate with a trained crisis counselor.
  • Stay with the person until professional help arrives.
  • Try to remove any weapons, medications, or other potentially harmful objects if it’s safe to do so.

If you or someone you know is having thoughts of suicide, a prevention hotline can help. The 988 Suicide and Crisis Lifeline is available 24 hours a day at 988. During a crisis, people who are hard of hearing can use their preferred relay service or dial 711 then 988.

Find more links and local resources.

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Jatenzo may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Is Jatenzo used for bodybuilding? If so, does taking the drug for this use cause certain side effects?

No, Jatenzo is not approved for use in bodybuilding. The Food and Drug Administration (FDA) has approved Jatenzo only for increasing testosterone levels in males* with testosterone deficiency.

Jatenzo has the potential for misuse in bodybuilding. With misuse, a drug is used in a way other than how a doctor prescribes it. Taking Jatenzo for reasons not prescribed, including higher dosages,† may lead to an increased risk of side effects. These include:

If you’re interested in bodybuilding, talk with your doctor about safe ways to reach your goals.

* Sex and gender exist on spectrums. Use of the term “male” in this article refers to sex assigned at birth.
† For information about Jatenzo’s recommended dosages for testosterone deficiency, view this article.

How do side effects of Jatenzo compare with those of testosterone cypionate injection?

Some Jatenzo side effects are similar to those of testosterone cypionate injection (Depo-Testosterone). Side effects they share include gynecomastia (breast enlargement), headache, low sperm count, and enlarged prostate.

Each drug also has its own unique side effects. For example, testosterone cypionate is an intramuscular injection, so side effects include pain at the injection site. (Jatenzo comes as a capsule that you swallow.) To learn more about side effects of testosterone cypionate injection, see this article.

For more information about how Jatenzo and testosterone injections compare, talk with your doctor or pharmacist.

Does Jatenzo cause hair loss?

No, Jatenzo isn’t expected to cause hair loss. There were no reports of hair loss in clinical trials of the drug.

However, hair loss may occur in males* who have low testosterone levels. Jatenzo is prescribed to help increase testosterone levels in males with testosterone deficiency.

Talk with your doctor if you have questions about what to expect with Jatenzo treatment.

* Sex and gender exist on spectrums. Use of the term “male” in this article refers to sex assigned at birth.

Learn more about some of the side effects that Jatenzo may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for Jatenzo.

Risk of increased blood pressure

Jatenzo has a boxed warning for increased blood pressure. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). It alerts doctors and patients about drug effects that may be dangerous.

Increased blood pressure was a common side effect in clinical trials of the drug. Blood pressure increases can result in high blood pressure, but this was rare in clinical trials.

Increased blood pressure doesn’t cause symptoms, but it can increase your risk of heart attack and stroke. A history of heart attack and stroke increases the risk of serious side effects from increased blood pressure with Jatenzo.

What you can do

Due to this risk, your doctor will check your blood pressure before recommending Jatenzo. They’ll also evaluate whether you have other risk factors for heart attack and stroke. These include diabetes, smoking, and obesity. If you have high blood pressure, your doctor will likely recommend medication to treat it. They’ll also advise whether Jatenzo is safe for you to take.

It’s important to monitor your blood pressure regularly while taking Jatenzo. One high reading may not be cause for concern, but tell your doctor if you have frequent high readings. If you develop high blood pressure, they may recommend medication to treat it. If you already take blood pressure medication, your doctor may adjust your treatment plan.

Increased red blood cell count

Increases in red blood cell (RBC) counts or hemoglobin levels may occur with Jatenzo treatment. Hemoglobin is a protein that RBCs need to carry oxygen throughout your body. High RBC counts can raise your risk of blood clots, stroke, and heart attack. Increased RBC count was rare in clinical trials of the drug.

Symptoms may include:

What you can do

If you develop any of the symptoms listed above, tell your doctor right away. If your RBC count is too high, your doctor may have you stop taking Jatenzo. This may be a temporary pause in treatment until your RBC count returns to its usual level. If needed, they may lower your Jatenzo dose or suggest a different medication for your condition.

Your doctor will monitor your RBC count and hemoglobin levels while you’re taking Jatenzo.

It’s important to complete all the lab and blood tests that your doctor requests. Talk with your doctor if you have questions about how Jatenzo may affect your blood cell counts.

Allergic reaction

As with most drugs, Jatenzo can cause an allergic reaction in some people. However, this side effect wasn’t reported in clinical trials.

Symptoms can be mild or serious and can include:

  • skin rash
  • itching
  • flushing
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What you can do

For mild symptoms of an allergic reaction, call your doctor right away. They may recommend ways to ease your symptoms and determine whether you should keep taking Jatenzo. However, if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Jatenzo has several precautions, including a boxed warning.

Boxed warning: Risk of increased blood pressure

This drug 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). For details, see the “Side effect specifics” section above.

Other precautions

Be sure to talk with your doctor about your health history before you take Jatenzo. This drug may not be the right treatment for you if you have certain medical conditions or other factors that affect your health. These are considered drug-condition or drug-factor interactions. The conditions and factors to consider include:

Increased red blood cell count. For details, see the “Side effect specifics” section above.

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

Enlarged prostate. Jatenzo may worsen an enlarged prostate. Be sure to tell your doctor if you have an enlarged prostate or experience any urinary symptoms. These may include increased frequency or inability to urinate. Your doctor will monitor you closely and suggest ways to treat these side effects. They may also consider a different medication than Jatenzo for your condition.

Liver or kidney problems. Jatenzo can cause certain side effects, such as hepatitis, edema (swelling), or chronic kidney disease. So if you have liver or kidney problems, tell your doctor before you begin taking Jatenzo. They’ll help determine whether Jatenzo is safe for you to take.

Heart condition. Taking Jatenzo can increase your risk of heart problems. Before starting Jatenzo, talk with your doctor about your heart health and any heart conditions you may have. They can help determine whether Jatenzo is safe for you to take.

Sleep apnea. Treatment with Jatenzo may increase your risk of sleep apnea. Your risk may be higher if you have other sleep apnea risk factors, such as chronic obstructive pulmonary disease (COPD), asthma, or obesity. Ask your doctor about your risk of sleep apnea and whether Jatenzo is the right treatment option for you.

Mental health conditions. Jatenzo may cause depression or suicidal thoughts or behaviors. Having a mental health condition such as anxiety may increase the risk of this side effect. So it’s important to talk with your doctor about your mental health before taking Jatenzo. If you have a mental health condition, your doctor can determine whether Jatenzo is right for you.

Pregnancy or breastfeeding. It’s not safe to take Jatenzo during pregnancy or while breastfeeding. Note that Jatenzo is not approved for use in females.*

Fertility. A reduction in fertility has occurred in some males* taking testosterone replacement therapy (TRT). Jatenzo is a type of TRT, so reduced fertility is possible from taking the drug. Due to this risk, talk with your doctor about your fertility before starting Jatenzo. They can advise whether it’s the right treatment option for you.

Alcohol consumption. If you drink alcohol, Jatenzo is likely safe for you. But alcohol can decrease testosterone levels. Your doctor may be able to advise an amount of alcohol that’s safe to consume while taking Jatenzo.

* Sex and gender exist on spectrums. Use of the terms “female” and “male” in this article refers to sex assigned at birth.

Most side effects with Jatenzo are rare, but some may be serious. Be sure to tell your doctor right away if you experience any of the side effects listed in the “Serious side effects” section above.

If you’d like to learn more about Jatenzo, talk with your doctor or pharmacist. They can help answer any questions you have about side effects from taking the drug.

Besides talking with your doctor, you can do some research on your own. These articles might help:

Disclaimer: Medical News Today 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.