Natesto (testosterone) is a brand-name nasal spray that’s prescribed to treat low testosterone in certain adults. As with other drugs, Natesto can cause side effects, such as headache, nosebleeds, or cough.

Natesto 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 in clinical trials:

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

Mild side effects that have been reported with Natesto include:

  • runny nose
  • nosebleed
  • headache
  • discomfort, dryness, or scabbing in your nose
  • increased level of PSA, which may be a sign of enlarged prostate or other conditions
  • sinus infection
  • upper respiratory tract infections, such as the common cold
  • bronchitis
  • changes in taste or smell
  • cough

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 and reviews side effects of the medication. If you develop a side effect while taking Natesto and want to tell the FDA about it, visit MedWatch.

Natesto may cause serious side effects, but they aren’t common. The list below may not include all possible serious side effects of the drug. For more information, you can refer to the Natesto prescribing information.

If you develop serious side effects while taking Natesto, 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:

  • serious blood clots in your legs or lungs, which may include symptoms such as:
    • chest pain
    • shortness of breath
    • swelling, warmth, tenderness, or pain in your leg
  • gynecomastia (enlarged breast tissue), which may include symptoms such as:
    • breast or nipple sensitivity
    • swelling or tenderness in breast gland tissue
  • liver problems, which may include symptoms such as:
    • yellowing of the skin or whites of the eyes
    • abdominal pain
    • nausea or vomiting
  • increased risk of heart attack or stroke, which may include symptoms such as:
    • chest pain
    • shortness of breath
    • slurred speech
    • sudden severe headache
  • sleep apnea, which may include symptoms such as:
    • pause in breathing during sleep
    • loud snoring
    • waking up several times during the night
    • not feeling rested
  • increased level of PSA, which may be a sign of enlarged prostate or other conditions
  • changes in lipids (fats in the blood, including cholesterol and triglycerides)
  • decreased sperm count
  • increase in red blood cells
  • edema (fluid buildup)

Some of these side effects are explained in more detail in the “Side effect specifics” section below.

ALLERGIC REACTION

For some people, Natesto nasal spray can cause an allergic reaction. But it’s not clear whether this side effect occurred in the drug’s studies.

In general, symptoms of allergic reaction can be mild or serious. You can learn more about possible symptoms in this article.

Ways to manage

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to Natesto nasal spray, your doctor may recommend taking a different medication instead.

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

Increase in red blood cells

Natesto can cause an increase in your red blood cell count. This was a rare but serious side effect reported in clinical studies of the drug.

Having too many red blood cells can make your blood thicker. This may raise your risk of a blood clot, heart attack, or stroke. Symptoms of a high red blood cell count may include:

What you can do

Your doctor will check your red blood cell count before you start therapy with Natesto. They’ll check it again after 3 to 6 months and then continue to check it once per year. If your red blood cell count is too high, your doctor will likely have you stop taking Natesto until it returns to the desired level.

If you have any symptoms listed above, talk with your doctor right away.

Edema

Edema (fluid buildup) is possible with Natesto, but it was not commonly reported in the drug’s clinical trials. Natesto causes your body to hold onto salt and water, causing a buildup of fluid in the body.

With mild edema, you can experience weight gain and swelling in your hands, ankles, or lower legs. Left untreated, serious edema can lead to fluid buildup in the lungs or brain and can be life threatening.

Fluid buildup is a problem for some people with liver, kidney, or heart problems, such as congestive heart failure (CHF). Taking Natesto can worsen fluid buildup and lead to serious health problems in these people. Get medical attention right away if you experience chest pain, difficulty breathing, or swelling in only one limb.

What you can do

Before taking Natesto, talk with your doctor about your personal risk of edema. You and your doctor can discuss the benefits and risks of Natesto therapy.

Your doctor will monitor you regularly for symptoms of edema while you’re taking Natesto. You can also watch for fluid changes and call your doctor if you experience any of the following:

Below is important information you should consider before taking Natesto.

Other precautions

Before taking Natesto, discuss your health history with your doctor. Natesto may not be right for you if you have certain medical conditions or other factors affecting your health. Be sure to talk with your doctor if any of the following apply to you:

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.