Important Mounjaro (tirzepatide) Safety Information

Important Safety Information for Mounjaro (tirzepatide) injection

Warning: Risk of Thyroid C-Cell Tumors

Mounjaro may cause tumors in the thyroid, including thyroid cancer. Watch for possible symptoms, such as a lump or swelling in the neck, hoarseness, trouble swallowing, or shortness of breath. If you have any of these symptoms, tell your healthcare provider.

  • Do not use Mounjaro if you or any of your family have ever had a type of thyroid cancer called medullary thyroid carcinoma (MTC).
  • Do not use Mounjaro if you have Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).

What is the FDA-approved use of Mounjaro?

Mounjaro® (mown-JAHR-OH) is an injectable medicine for adults with type 2 diabetes used along with diet and exercise to improve blood sugar (glucose).

Limitations of Use:

  • It is not known if Mounjaro can be used in people who have had inflammation of the pancreas (pancreatitis). Mounjaro is not for use in people with type 1 diabetes. It is not known if Mounjaro is safe and effective for use in children under 18 years of age.

Who should not use Mounjaro?

Do not use Mounjaro if:

  • You or any of your family have ever had a type of thyroid cancer called medullary thyroid carcinoma (MTC) or if you have an endocrine system condition called Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
  • You have a known allergic reaction to Mounjaro.

How should I take Mounjaro?

You can take Mounjaro with or without food. The pre-filled injector pen is self-administered as a subcutaneous injection in the stomach, thigh, or upper arm once a week on the same day every week.  You should change your injection site each week.  Do not use the same site for each injection. Your Ivím provider will guide you on a treatment regimen that may include an increase in dose every four weeks.

You should not change your dosing regimen or stop taking Mounjaro as prescribed without discussing with your provider first.  If you take too much Mounjaro, call your healthcare provider or seek medical advice promptly.

What should I discuss with my Ivím provider before using Mounjaro?

  • Mounjaro has certain drug interactions. It’s important to tell your Ivím provider all of the medications you are currently taking, including prescription, over-the-counter medications, vitamins, and herbal and dietary supplements.
  • Your healthcare provider should show you how to use Mounjaro before you use it for the first time.
  • Talk to your healthcare provider about low blood sugar and how to manage it.
  • If you take birth control pills by mouth, talk to your healthcare provider before you use Mounjaro. Birth control pills may not work as well while using Mounjaro. Your healthcare provider may recommend another type of birth control for 4 weeks after you start Mounjaro and for 4 weeks after each increase in your dose of Mounjaro.

Some medications to watch out for include:

  • Medications for diabetes: Medications used to treat type 1 or type 2 diabetes, including insulin or sulfonylureas (such as Amaryl or Glucotrol XL)
  • Other oral medications: Mounjaro causes a delay in gastric emptying, so it has the potential to impact the absorption of medications that are taken by mouth at the same time. Your provider can guide you on how to schedule your medications.
  • Hormonal birth control: If you are using an oral hormonal contraceptive (birth control), Mounjaro may decrease its efficacy, especially after the first dose. Switch to a non-oral contraceptive method or use a barrier method of contraception for 4 weeks after starting Mounjaro and for 4 weeks after each dose escalation, until you reach a maintenance dose.
  • Other GLP-1 medications: Including Zepbound, Wegovy, Ozempic, Saxenda, Victoza, Byetta, Bydureon, or compound GLP-1 formularies. These medications should not be taken with Mounjaro.
  • Other products for weight loss: Including dietary supplements
  • It’s important to share your entire medical history with your provider. In particular, tell your provider if you have a past history of:
  • Type 1 or type 2 diabetes
  • Thyroid cancer
  • Gastrointestinal disease
  • Pancreatitis
  • Kidney disease
  • Diabetic retinopathy
  • Depression
  • Suicidal thoughts or behavior
  • Tell your provider if you are pregnant, planning to become pregnant, or breastfeeding. 
  • If you are pregnant: Mounjaro should not be used during pregnancy. Based on animal studies, there may be potential risks to an unborn baby from exposure to Mounjaro during pregnancy. There is no benefit to weight loss during pregnancy and it may cause harm to the unborn baby.
  • If you are a female reproductive potential: Mounjaro may reduce the efficacy of oral hormonal contraceptives. Switch to a non-oral contraceptive method, or add a barrier method of contraception for 4 weeks after starting medication and for 4 weeks after each dose escalation until you reach a maintenance dose.
  • If you are breastfeeding: It is not known if Mounjaro passes into breast milk. Talk to your provider first about the benefits and risks of using Mounjaro while breastfeeding.
  • Pregnancy registry: There will be a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to Mounjaro during pregnancy. Pregnant patients exposed to Mounjaro and healthcare providers are encouraged to contact Eli Lilly and Company at 1-800-LillyRx (1-800-545-5979).

Withholding or providing inaccurate information about your health and medical history in order to obtain treatment may result in harm, including, in some cases, death.

What are the most serious side effects that I or a caregiver should monitor for when taking Mounjaro?

If you are experiencing a medical emergency, call 911 or seek immediate medical attention.

These serious side effects are rare, but can occur with Mounjaro. You or a caregiver should carefully monitor for these side effects, especially in the beginning of treatment and with dose changes.

  • Thyroid C-Cell Tumors: In rats, Mounjaro caused a dose-dependent and treatment-duration-dependent increase in thyroid C-cell tumors. It is unknown whether Mounjaro causes thyroid C-cell tumors in humans. Mounjaro is contraindicated in patients with a family history of medullary thyroid cancer (MTC) or in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Tell your provider if you get a lump or swelling in your neck, hoarseness, trouble swallowing, or shortness of breath. These may be symptoms of thyroid cancer.
  • Severe Gastrointestinal Disease: Mounjaro is associated with gastrointestinal side effects, such as nausea, diarrhea, vomiting, constipation, and stomach pain, and can sometimes be severe. It hasn’t been studied in patients with severe gastrointestinal disease and isn’t recommended in these patients. The majority of nausea, vomiting, and/or diarrhea eventsoccurred during a dose increase and decreased over time.
  • Inflammation of the pancreas (pancreatitis). Stop using Mounjaro and call your healthcare provider right away if you have severe pain in your stomach area (abdomen) that will not go away, with or without vomiting. You may feel the pain from your abdomen to your back.
  • Low blood sugar (hypoglycemia). Your risk for getting low blood sugar may be higher if you use Mounjaro with another medicine that can cause low blood sugar, such as a sulfonylurea or insulin. Signs and symptoms of low blood sugar may include dizziness or light-headedness, sweating, confusion or drowsiness, headache, blurred vision, slurred speech, shakiness, fast heartbeat, anxiety, irritability, or mood changes, hunger, weakness and feeling jittery.
  • Serious allergic reactions. Stop using Mounjaro and get medical help right away if you have any symptoms of a serious allergic reaction, including swelling of your face, lips, tongue or throat, problems breathing or swallowing, severe rash or itching, fainting or feeling dizzy, and very rapid heartbeat.
  • Kidney problems (kidney failure). In people who have kidney problems, diarrhea, nausea, and vomiting may cause a loss of fluids (dehydration), which may cause kidney problems to get worse. It is important for you to drink fluids to help reduce your chance of dehydration.
  • Severe stomach problems. Stomach problems, sometimes severe, have been reported in people who use Mounjaro. Tell your healthcare provider if you have stomach problems that are severe or will not go away.
  • Changes in vision. Tell your healthcare provider if you have changes in vision during treatment with Mounjaro.
  • Gallbladder problems. Gallbladder problems have happened in some people who use Mounjaro. Tell your healthcare provider right away if you get symptoms of gallbladder problems, which may include pain in your upper stomach (abdomen), fever, yellowing of skin or eyes (jaundice), and clay-colored stools.
  • Diabetic Retinopathy Complications in Patients with a History of Diabetic Retinopathy: Rapid improvement of glucose control has been associated with temporary worsening of diabetic retinopathy. Tell your provider right away if you experience changes in vision.
  • Suicidal Behavior and Ideation: You should pay attention to any mental health changes, especially sudden changes in your mood, behaviors, thoughts, or feelings. Call your healthcare provider right away if you have any mental changes that are new, worse, or worry you.
  • Never Share a Pen: Pen-sharing poses a risk of infection.

What are the most common side effects of Mounjaro?

  • Nausea
  • Diarrhea
  • Vomiting
  • Constipation
  • Stomach pain
  • Indigestion
  • Injection site reactions
  • Feeling tired
  • Allergic reactions
  • Belching
  • Hair loss
  • Gastroesophageal reflux disease (heartburn)

You are encouraged to report negative side effects of prescription products to the FDA. Visit or call 1-800-FDA-1088.

This information is not comprehensive. Please see the full Prescribing Information for complete safety information.