Key takeaways

  • The most common side effects you may experience with Mounjaro include nausea, vomiting, diarrhea, constipation, and stomach pain. These side effects typically go away on their own within a few weeks as your body adjusts to treatment.
  • Mounjaro carries a boxed warning (the most serious type of FDA warning) for thyroid cancer risk. Doctors typically won’t prescribe Mounjaro 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.

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

Mounjaro can cause certain side effects, some more common than others. These side effects may be temporary, lasting a few days to weeks. Talk with your doctor if side effects do not go away, get worse, or become too difficult to tolerate.

Mounjaro’s commonly reported side effects 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.

Experiencing side effects? 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 this drug and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

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:

Note: It’s important not to share your Mounjaro pen with anyone, even if you change the needle. Sharing injection devices increases the risk of developing a bloodborne disease, like hepatitis C.

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.

Allergic reaction

For some people, Mounjaro can cause an allergic reaction. But it’s not clear how often allergic reactions were reported in Mounjaro’s studies.

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 and can determine whether you should keep using Mounjaro.

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 Mounjaro, they may have you switch to a different treatment.

Long-term side effects from Mounjaro are possible, but not common.

Most mild side effects of Mounjaro only last a few days or weeks as your body gets used to the drug. Other more serious side effects may last for a longer time.

Long-term side effects seen in Mounjaro’s studies include serious digestive problems and pancreatitis. These effects could persist even after you stop using Mounjaro. In some cases, they may require treatment to resolve completely.

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.

There may be things you can do to help make certain Mounjaro side effects more manageable. If you have ongoing, worsening, or bothersome side effects, talk with your doctor or pharmacist. They can suggest tips for managing them or recommend other available treatment options for your condition.

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 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.

Gastrointestinal issues

Gastrointestinal problems were among the most common side effects reported in Mounjaro’s studies. This includes side effects such as:

  • diarrhea
  • constipation
  • nausea and vomiting
  • appetite loss
  • abdominal pain

Gastrointestinal issues with Mounjaro can range from mild to severe. They’re most common after dosage increases and typically resolve on their own. However, it’s possible for these issues to continue for as long as you use Mounjaro.

Some of these side effects, such as severe diarrhea, can lead to dehydration. This can cause or worsen kidney problems, including acute kidney injury (AKI) in serious 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 bothersome or severe symptoms you have. They can determine how to manage any side effects you experience. 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.

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.

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

Mounjaro does not have FDA approval for non-diabetic conditions, such as 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.

» Learn more: Mounjaro for Weight Loss

Mounjaro slows the passage of food through your stomach, so you may experience some digestive side effects after eating. Some of Mounjaro’s more commonly reported side effects include:

  • diarrhea
  • constipation
  • nausea and vomiting
  • appetite loss
  • abdominal pain

If you are concerned about Mounjaro’s side effects, talk with your doctor or pharmacist. They can suggest ways to help you manage them.

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. To learn more, see the “Side effects explained” section.

Other warnings

Before taking Mounjaro, discuss your health history with your doctor. Mounjaro 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:

  • kidney problems
  • 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)
  • previous allergic reaction to Mounjaro or any of its ingredients
  • pregnancy
  • breastfeeding

Disclaimer: While Healthline strives for factual, comprehensive, and current information, this article is not a substitute for a licensed healthcare professional’s expertise. Always consult a doctor before taking or discontinuing any medication. Drug information is subject to change and may not cover all uses, directions, precautions, warnings, interactions, reactions, or adverse effects. The lack of a warning does not guarantee a drug’s safety, effectiveness, or appropriateness for all patients or specific uses. Learn more about our approach to content integrity.