Key takeaways

  • Mounjaro (tirzepatide) is a brand-name injection prescribed for type 2 diabetes in people ages 10 years and older. As with other drugs, Mounjaro can cause side effects, such as nausea, diarrhea, and appetite loss.
  • Many side effects of Mounjaro are temporary and expected to go away on their own. However, Mounjaro may also cause long-term side effects.
  • Side effects of Mounjaro are most common at the start of treatment and after a dosage adjustment. Your doctor may adjust your dose slowly over time to help reduce the risk of certain side effects.

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 effect specifics” section.

Mounjaro 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 Mounjaro in clinical trials:

  • nausea
  • diarrhea
  • loss of appetite
  • vomiting
  • constipation

Mild side effects of Mounjaro

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

Mild side effects that have been reported with Mounjaro include:

  • mild digestive system problems, such as:
    • nausea
    • diarrhea
    • vomiting
    • constipation
  • loss of appetite
  • indigestion
  • abdominal pain or stomach pain
  • burping
  • flatulence
  • acid reflux and heartburn
  • abdominal swelling
  • mild injection site reaction, such as pain

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. Sharing your experience helps make medications 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 taking Mounjaro and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

Mounjaro may cause serious side effects. The following list may not include all possible serious side effects of the drug. For more information, you can refer to Mounjaro’s prescribing information.

If you develop serious side effects while using Mounjaro, 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 include:

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

Allergic reaction

For some people, Mounjaro can cause an allergic reaction. However, this side effect was rarely reported in clinical trials.

In general, symptoms of an allergic reaction can be mild or serious.

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 receiving the medication.

For severe allergic reaction symptoms, such as swelling or difficulty 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 Mounjaro, your doctor may recommend taking a different medication instead.

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

Risk of thyroid cancer

Mounjaro has a boxed warning from the Food and Drug Administration (FDA) regarding a risk of thyroid cancer. Boxed warnings alert doctors and patients about the most serious side effects certain drugs may cause.

Animal studies of tirzepatide (the active ingredient in Mounjaro) showed an increased risk of certain thyroid cancers. This includes a type of cancer called medullary thyroid carcinoma (MTC). However, animal studies don’t always predict how a medication will affect humans. It isn’t currently known whether Mounjaro also increases the risk of thyroid cancer in people.

Symptoms of thyroid cancer include:

What you can do

If you have a personal or family history of MTC, tell your doctor before starting treatment with this drug. Due to this risk, they typically won’t prescribe Mounjaro or a similar drug for your condition. Additionally, they usually won’t prescribe Mounjaro if you have a type of cancer called multiple endocrine neoplasia syndrome type 2 (MEN2).

If you notice any of the symptoms mentioned earlier during treatment, talk with your doctor right away. During treatment, your doctor will also monitor your condition for symptoms of thyroid cancer. If you have symptoms of thyroid cancer, they can order tests to check for this condition. They’ll also discuss whether it’s safe for you to continue Mounjaro treatment. If they decide it’s not safe, they can discuss whether a different diabetes treatment may be safer.

Severe digestive system problems

It’s possible to develop certain digestive system problems as a side effect of Mounjaro. In clinical trials, these were the most commonly reported side effects of Mounjaro. Examples of potential digestive problems reported with Mounjaro include nausea, diarrhea, constipation, vomiting, and slowed emptying of the stomach.

These side effects are typically mild. However, in rare cases, these digestive system problems can be severe.

Severe digestive system problems can lead to dehydration, which can cause acute kidney injury (AKI). Symptoms of AKI include weakness, less frequent urination, and confusion.

What you can do

If you experience digestive system problems during treatment with Mounjaro, contact your doctor right away. Your doctor can review your symptoms and recommend the best way to treat them.

Depending on the severity of your digestive system problems, your doctor may suggest stopping treatment with Mounjaro.

If you think you’re experiencing symptoms of AKI, seek urgent medical care. This condition requires prompt treatment to help protect your kidneys and return their function to usual. Without immediate treatment, AKI can cause serious kidney damage.

Gallbladder problems

It’s possible to develop gallbladder problems during treatment with Mounjaro. In clinical trials, people reported problems such as bile duct blockage and gallstones.

Symptoms of gallstones or bile duct blockage can include:

What you can do

If you experience any of the symptoms mentioned previously of gallbladder problems, talk with your doctor right away. They can order tests to check how well your gallbladder is functioning.

If you do have gallbladder problems, your doctor will advise whether it’s safe for you to continue Mounjaro treatment. They’ll also suggest the best way to address your gallbladder symptoms.

It’s possible for Mounjaro to cause some long-term side effects, such as digestive problems, kidney problems, gallbladder problems, and pancreatitis. These side effects could last for a long time and require long-term treatment. They weren’t common in clinical trials, but they are possible.

How long do Mounjaro’s side effects last?

It depends. Some of Mounjaro’s side effects may be temporary and last a few days or weeks. For example, mild side effects such as nausea or diarrhea may go away after your body gets used to the drug.

Other side effects may last longer or require long-term treatment, especially if they’re serious.

To minimize your risk of side effects and help your body get used to the drug, your doctor will start you on the lowest Mounjaro dose and increase your dose gradually.

Talk with your doctor to learn more about possible side effects of Mounjaro and how long they may last. If you’re experiencing a side effect that’s long lasting, bothersome, or severe, be sure to talk with your doctor.

There are certain precautions to consider and discuss with your doctor before starting treatment with Mounjaro.

Boxed warning: Risk of thyroid cancer

Mounjaro has a boxed warning for the possible risk of thyroid cancer. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). For details, see the “Side effect specifics” section.

Other precautions

Before using 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:

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

Hair loss was not reported in Mounjaro’s clinical trials.  However, some people may experience hair shedding, which can be related to rapid weight loss from improved blood sugar levels in people using the drug to treat type 2 diabetes.

When the body loses weight quickly, it may trigger a condition called telogen effluvium, where a large number of hair follicles enter their resting phase at the same time and then shed. Typically, this type of hair loss is temporary.

If you have questions or concerns about hair loss, talk with your doctor.

Mounjaro has FDA-approval to treat type 2 diabetes. But doctors may prescribe the drug off-label for weight loss and weight management. (Off-label drug use is when an FDA-approved drug is prescribed for a purpose other than what it’s approved for.)

The most common side effects of Mounjaro in people without type 2 diabetes are expected to be similar to the most common side effects in people with type 2 diabetes. Those include digestive side effects, such as:

  • nausea
  • diarrhea
  • loss of appetite
  • vomiting
  • constipation

For more information about Mounjaro’s side effects, talk with your doctor or pharmacist.

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.