Key takeaways

  • The most common side effects you may experience with Mounjaro include nausea, vomiting, diarrhea, decreased appetite, constipation, and abdominal pain.
  • Mounjaro carries a boxed warning (the most serious FDA warning) for thyroid cancer risk, and you may not be prescribed it if you have multiple endocrine neoplasia syndrome type 2 or a personal or family history of medullary thyroid cancer.
  • While side effects like nausea and diarrhea may be temporary as your body adjusts, serious effects such as pancreatitis and severe digestive issues may require long-term treatment.

Mounjaro (tirzepatide) is prescribed to help manage blood sugar levels in adults with type 2 diabetes, along with a balanced diet and exercise.

To learn more about Mounjaro, including its uses, dosage, and cost, refer to this Mounjaro overview article.

Mounjaro has a boxed warning. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). For details, see the “Side effects explained” section.

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

Many common side effects of Mounjaro are mild and may not require medical attention.

Examples of mild side effects that have been reported with Mounjaro 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 bothersome, talk with your doctor or pharmacist. And do not stop using Mounjaro unless your doctor recommends it.

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

For more information about some of these side effects, see the “Side effects explained” section.

It’s possible to have serious side effects from Mounjaro, but they’re not common.

Serious side effects that have been reported with this drug include:

For more information about some of these side effects, see the “Side effects explained” section.

If you develop serious side effects during Mounjaro treatment, 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.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. Sharing your experience helps make medication safer for everyone by giving doctors and researchers more information about how the drug works in real life. If you develop a side effect while using Mounjaro and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

It varies. Some side effects may last just a few days or a few weeks. Mild side effects such as diarrhea or nausea may go away after your body gets used to Mounjaro.

Other side effects, such as serious side effects, may last for a longer time. Long-term side effects seen in Mounjaro’s studies include serious digestive problems and pancreatitis.

In studies, these side effects were not common. But if they occur, these side effects could last a long time and need long-term treatment.

For more information about how long side effects of Mounjaro might last, or if you’re experiencing long-term side effects, talk with your doctor.

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

What are Mounjaro’s side effects when used for weight loss?

Mounjaro is not FDA-approved to be used for weight loss: However, your doctor may prescribe it off-label for this purpose. With off-label use, your doctor prescribes a drug for a purpose other than what it’s approved for. Mounjaro is approved to treat type 2 diabetes.

Mounjaro’s side effects when used for weight loss are expected to be similar to side effects of the drug when it’s used for type 2 diabetes. Examples of commonly reported side effects include nausea, vomiting, abdominal pain, and diarrhea. See “What are the mild side effects of Mounjaro?” and “What are the serious side effects of Mounjaro?” to learn what side effects were reported in studies.

To learn more, you can refer to this Mounjaro for weight loss article.

Note: The FDA has recently approved Zepbound to help with weight loss in certain people. Zepbound is a new prescription medication that contains the same active drug (tirzepatide) as Mounjaro and is approved for weight loss. Your doctor may prescribe this drug instead of Mounjaro for weight loss. Be sure to discuss Zepbound with your doctor if you’d like more information.

Does Mounjaro make you tired?

In Mounjaro’s studies, tiredness was not reported. But it’s possible that tiredness or fatigue (low energy) could occur as a symptom of certain side effects of Mounjaro. Examples include decreased appetite, nausea, vomiting, and pancreatitis.

It’s also possible to develop low blood sugar if you use Mounjaro with other diabetes medications. Feeling tired can be a symptom of low blood sugar.

If you feel unusually tired during Mounjaro treatment, talk with your doctor. They can help identify the cause. They can also suggest ways to manage any side effects from the drug that you may be experiencing.

Does Mounjaro cause dehydration?

Dehydration was not reported as a direct side effect in Mounjaro’s studies. It’s possible to become dehydrated while using this medication, but it’s rare.

Dehydration can occur because nausea, vomiting, and diarrhea are common side effects of this drug. In most cases, these side effects are mild, but in rare cases, they can be severe. And severe vomiting and diarrhea can lead to dehydration, which may result in kidney problems.

Tell your doctor right away if you have vomiting or diarrhea that does not stop. They can recommend ways to manage these side effects. If needed, they can also provide treatment for dehydration.

Does Mounjaro cause back pain?

No. Mounjaro shouldn’t cause back pain. This side effect wasn’t reported in the drug’s studies.

But certain side effects of Mounjaro may have back pain as a symptom. For example, pancreatitis is a potential side effect of Mounjaro. Symptoms of pancreatitis can include:

If you develop symptoms of pancreatitis while using Mounjaro, let your doctor know right away. They’ll order tests to determine the cause of your symptoms. If they confirm that you have pancreatitis, you’ll likely need to go to the hospital for treatment and stop using Mounjaro.

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

Diarrhea

Diarrhea was one of the most common side effects in Mounjaro’s studies. Diarrhea can range from mild to severe.

In studies, people reported diarrhea after their Mounjaro dosage was increased. However, over time, the diarrhea went away, and the severity decreased. The same was reported for nausea and vomiting, which are also possible side effects of Mounjaro.

Severe diarrhea can lead to dehydration. This can cause or worsen kidney problems, including acute kidney injury (AKI) in severe cases. AKI can cause weakness, confusion, and less frequent urination.

What might help

If you experience diarrhea or other digestive problems with Mounjaro, be sure to drink plenty of fluids and take other steps at home to care for yourself. Tell your doctor about any diarrhea or other symptoms you have. They can determine how severe they are and how to manage them. Your doctor might lower your dose or, in severe cases, have you stop Mounjaro treatment.

If you might be experiencing AKI symptoms, get medical care immediately by calling 911 (or your local emergency number) or going to the nearest hospital or emergency room. This condition requires fast treatment to protect your kidneys from further damage.

Risk of thyroid cancer

Mounjaro has a boxed warning for the risk of thyroid cancer. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).

Using Mounjaro may increase your risk of developing thyroid cancer. Mounjaro caused thyroid cancer in animals given this drug in studies. But it’s not clear whether Mounjaro could cause thyroid cancer, such as medullary thyroid cancer (MTC), in humans.

Due to this risk, doctors will not prescribe Mounjaro if you have multiple endocrine neoplasia syndrome type 2 (MEN 2, which is a rare condition that causes thyroid tumors). They also won’t prescribe Mounjaro if you or a family member has had MTC.

What might help

During your Mounjaro treatment, your doctor may occasionally order blood tests or an ultrasound to check for signs of thyroid cancer. Let them know if you have symptoms of thyroid cancer during your treatment, including:

Your doctor will likely have you temporarily stop Mounjaro if you have any of these symptoms. If they confirm that you have thyroid cancer, they’ll likely have you permanently stop Mounjaro treatment. In this case, they’ll recommend a different medication for your diabetes.

Injection site reaction

It’s possible to have an injection site reaction with Mounjaro. This side effect was reported in the drug’s studies. Symptoms at the injection site include:

  • pain
  • swelling
  • redness or other skin color changes

What might help

Injection site reactions with Mounjaro are usually mild and go away on their own.

If you have an injection site reaction, applying an ice pack to the area after your injection may help relieve pain and swelling. Changing the site where you inject the drug each time can also help you avoid injection site reactions. You can inject Mounjaro into your abdomen, the top of your thigh, or the back of your upper arm.

Let your doctor know if you have bothersome or painful injection site reactions with Mounjaro. They can discuss injection techniques with you that can help prevent these side effects.

They may also recommend over-the-counter (OTC) pain relievers, such as ibuprofen (Advil, Motrin) or acetaminophen (Tylenol). But always talk with your doctor or pharmacist before taking any OTC drugs to be sure they’re safe for you.

Allergic reaction

Like most drugs, Mounjaro can cause an allergic reaction in some people. Symptoms can be mild to serious.

A mild allergic reaction can cause:

A more severe allergic reaction is rare but possible. This is called anaphylaxis. Symptoms can include:

  • 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:

  • an antihistamine you swallow, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Mounjaro, they’ll decide whether you should continue using it.

If you have symptoms of a severe allergic reaction, such as swelling or difficulty 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 Mounjaro, they’ll likely have you switch to a different treatment.

Mounjaro may not be safe for everyone. The drug comes with several warnings, including a boxed warning.

Boxed warning: Risk of thyroid cancer

Mounjaro has a boxed warning for the risk of thyroid cancer. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Side effects explained” section.

Other warnings

Mounjaro 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 this drug is a good treatment option for you.

Talk with your doctor about your health history before starting Mounjaro. Factors to consider include:

  • kidney problems
  • previous allergic reaction to Mounjaro or any of its ingredients
  • pancreatitis
  • severe digestion problems, including severe gastroparesis
  • diabetic retinopathy
  • any upcoming procedures or surgeries (Mounjaro may increase the risk of pulmonary aspiration, so it’s important that your doctors and healthcare professionals know you’re using it)

Alcohol and Mounjaro

There are no known interactions between alcohol and Mounjaro. But keep in mind that alcohol can cause some of the same side effects as Mounjaro, such as:

  • nausea
  • vomiting
  • diarrhea

Consuming alcohol during your Mounjaro treatment may increase your risk of these side effects or worsen them if they occur.

Alcohol can also increase the risk of low blood sugar in people with diabetes. And alcohol can mask the symptoms of hypoglycemia, a potential side effect of Mounjaro. So drinking alcohol during Mounjaro treatment may cause your blood sugar to become too low. And this condition can be serious, even life threatening, if it’s not treated right away.

If you drink alcohol, talk with your doctor about how much, if any, is safe to consume with this drug.

Pregnancy and breastfeeding while using Mounjaro

It’s not known whether Mounjaro is safe to use during pregnancy. Studies have not been conducted with pregnant people using Mounjaro. Let your doctor know if you’re pregnant or planning to become pregnant before starting this drug. They may recommend a different treatment option for you.

It’s not known whether Mounjaro passes into breast milk or what effect it might have on a child who is breastfed. Before starting Mounjaro treatment, talk with your doctor if you’re breastfeeding or planning to do so. They’ll talk with you about safe ways to feed your child.

You can also refer to this Mounjaro and reproductive health article for details.

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.