Mounjaro (tirzepatide) is a brand-name injection that’s prescribed for type 2 diabetes in adults. As with other drugs, Mounjaro can cause side effects, such as nausea, diarrhea, and appetite loss.

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:

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:

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 Mounjaro and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Side effect specifics” below.

Mounjaro may cause serious side effects. The list below 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 taking 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 this side effect, see “Side effect specifics” below.
† Mounjaro has a boxed warning for this side effect. This is a serious warning from the Food and Drug Administration (FDA). To learn more, see the “Side effect specifics” section below.
‡ To learn more, see the “Side effect specifics” section below.

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

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, especially if they’re serious. Examples of long-term side effects reported in Mounjaro’s clinical trials include:

  • severe digestive problems, which may lead to acute kidney injury
  • pancreatitis

These side effects weren’t common in clinical trials, but they are possible. These side effects could last for a long time and require long-term treatment.

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 or is bothersome or severe, be sure to talk with your doctor.

Does Mounjaro make you tired?

Tiredness or fatigue were not reported in Mounjaro’s clinical trials. However, it’s possible for certain side effects of Mounjaro to cause you to feel tired. For example, experiencing nausea, vomiting, appetite loss, or pancreatitis can cause you to feel tired.

It’s also possible that taking Mounjaro with other diabetes medications can lead to low blood sugar, and tiredness can be a symptom of low blood sugar.

If you’re feeling tired during Mounjaro treatment, discuss this with your doctor. They can help determine possible causes and ways to help reduce your fatigue.

Can Mounjaro cause kidney problems?

It’s possible. Kidney problems weren’t reported in clinical trials of Mounjaro.

However, Mounjaro belongs to a class of drugs called glucagon-like peptide-1 (GLP-1) receptor agonists. Kidney problems have been reported with other GLP-1 receptor agonists.

In addition, some of Mounjaro’s side may increase your risk of acute kidney injury (AKI). These side effects include nausea, vomiting, and diarrhea, which can lead to dehydration. In turn, severe dehydration can cause AKI. Symptoms of AKI include weakness, less frequent urination, and confusion.

For more information about kidney problems and Mounjaro, talk with your doctor or pharmacist.

Is low blood sugar a side effect of Mounjaro?

No, hypoglycemia (low blood sugar) isn’t an expected side effect of Mounjaro alone. In clinical trials, it wasn’t reported when Mounjaro was used on its own to treat type 2 diabetes.

However, low blood sugar was reported when Mounjaro was used in combination with certain other type 2 diabetes drugs. These other medications include sulfonylureas, such as Glucotrol XL (glipizide). They also include insulins, such as Tresiba (insulin degludec) or NovoLog and Fiasp (insulin aspart).

Symptoms of low blood sugar include:

Before you start treatment with Mounjaro, tell your doctor about any medications you’re taking. It’s especially important to discuss any other medications you take for type 2 diabetes.

If you’re taking a sulfonylurea or insulin drug, your doctor may lower your dose of that drug. This can help reduce your risk of low blood sugar during Mounjaro treatment.

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 drug 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 or have had a type of cancer called multiple endocrine neoplasia syndrome type 2 (MEN2).

If you notice any of the above symptoms 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 type 2 diabetes treatment may be safer.

Severe digestive problems

It’s possible to develop certain digestive problems as a side effect of Mounjaro. In clinical trials, these were the most commonly reported side effects of Mounjaro. Rarely, these digestive problems can be severe.

Examples of potentially severe digestive problems reported with Mounjaro include nausea, diarrhea, and vomiting.

Severe digestive 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 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 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 above symptoms 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, they’ll advise whether it’s safe for you to continue Mounjaro treatment. They’ll also suggest the best way to address your gallbladder symptoms.

Pancreatitis

It’s possible for Mounjaro to cause pancreatitis (swelling and inflammation in your pancreas). In the drug’s clinical trials, this side effect was reportedly rare. In serious cases, pancreatitis can be life threatening.

Symptoms of pancreatitis can include vomiting and severe abdominal pain, which may spread to your back.

It isn’t known whether your risk of this side effect is higher if you’ve had pancreatitis in the past.

What you can do

If you think you have symptoms of pancreatitis, immediately contact your doctor. They’ll likely have you stop treatment with Mounjaro. They can also recommend the best treatment for your pancreatitis symptoms. If your symptoms feel severe or life threatening, seek emergency medical care, such as calling 911 or going to the closest emergency room.

Allergic reaction

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

Symptoms of a mild allergic reaction can include:

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

  • 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 Mounjaro. However, if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

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

Boxed warning: Risk of thyroid cancer

This drug has a boxed warning for the risk of thyroid cancer. This is a 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 start treatment with Mounjaro. 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:

Diabetic retinopathy. Before starting Mounjaro treatment, tell your doctor if you have diabetic retinopathy (an eye condition caused by diabetes). It’s possible for Mounjaro to temporarily worsen your condition. This is most likely to happen when you first start treatment with the drug. If you experience vision changes during treatment, including blurry vision, contact your doctor.

Digestive problems. The most common side effects with Mounjaro are digestive problems, such as nausea, diarrhea, and constipation. Before starting treatment, tell your doctor if you have an existing digestive condition, such as diabetic gastroparesis (slowed stomach emptying). Mounjaro may increase the risk of digestive problems or cause them to be more severe. Your doctor can determine whether Mounjaro is safe for your condition.

Pancreatitis. It’s possible for Mounjaro injections to cause pancreatitis (swelling and inflammation in your pancreas). It isn’t known whether your risk of this side effect is higher if you’ve had pancreatitis in the past. If you have or have had pancreatitis, tell your doctor before starting Mounjaro treatment. They can determine whether Mounjaro is a safe treatment for your type 2 diabetes.

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

Alcohol with Mounjaro

There are no known interactions between Mounjaro and alcohol.

However, if you have diabetes, drinking alcohol may cause hyperglycemia (high blood sugar) or hypoglycemia (low blood sugar). (Mounjaro is prescribed to help manage blood sugar levels in adults with type 2 diabetes.)

In addition, drinking alcohol can make it harder to notice symptoms of these conditions. For these reasons, your doctor may suggest limiting alcohol consumption during treatment.

If you have questions about drinking alcohol while taking Mounjaro, talk with your doctor or pharmacist.

Pregnancy and breastfeeding while taking Mounjaro

It’s not known whether it’s safe to take Mounjaro during pregnancy. However, having unmanaged diabetes during pregnancy may increase the risk of preterm labor and pregnancy loss.

If you’re pregnant or planning to become pregnant, talk with your doctor. They can advise you on safe ways to treat your diabetes during pregnancy.

It also isn’t known whether it’s safe to breastfeed during Mounjaro treatment. If you’re breastfeeding or planning to breastfeed, let your doctor know. They can explain the risks and benefits of breastfeeding during treatment. If necessary, they can also advise you on safe feeding options for your child.

While Mounjaro can cause side effects, they’re usually mild and go away with continued treatment. Serious side effects from Mounjaro are rare but can occur.

If you’d like to learn more about Mounjaro, 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:

  • More information about Mounjaro. For details about other aspects of Mounjaro, refer to this article.
  • Cost. If you’d like to learn about Mounjaro and cost, see this article.
  • Dosage. For information about the dosage of Mounjaro, view this article.
  • Interactions. To find out about Mounjaro’s interactions, see this article.
  • Reproductive health. For details about Mounjaro and pregnancy, breastfeeding, and birth control, view this article.
  • A look at type 2 diabetes. For details about type 2 diabetes, see our diabetes hub.

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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.