Tirzepatide (Mounjaro): uses, doses, and side effects

If you are one of the 37 million Americans with diabetes, you know that controlling your blood sugar isn’t always easy (CDC, 2021). Fortunately, many strategies are available to help you achieve healthy blood sugar levels and prevent serious health complications from diabetes.

Tirzepatide is the latest prescription treatment option for type 2 diabetes in adults. Read on to learn more about tirzepatide, its side effects, dosage, and potential to help with weight loss.

Tirzepatide (brand name Mounjaro) is a new diabetic medication (it got FDA approval in May 2022) that you inject once a week (FDA, 2022). 

Mounjaro is not a type of insulin. It belongs to a new class of drugs called dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist. It differs from GLP-1 receptor agonists like semaglutide (Ozempic; Wegovy) because it also affects GIP. (We’ll explain what this means in the next section.)

Mounjaro comes in a single-dose injector pen. You can store the pens in the refrigerator or keep them unrefrigerated for up to 3 weeks (at temperatures under 86°F or 30°C). So, it is convenient to travel with this medication if necessary.

When you eat, your body naturally makes hormones called incretins. Normally, incretins help your body keep your blood sugar levels within a healthy range. Incretins signal your pancreas to release insulin, which scientists call the incretin effect. (Insulin signals your body to move sugar out of the blood and into your cells). Incretins also play a role in helping you feel full (Collins, 2022). 

However, the incretin effect is diminished in people with type 2 diabetes (Boer, 2020). This leads to high blood sugar levels, which can be challenging to control. Over time, high blood sugar can damage the nerves, kidneys, and eyes, and raises the risk of serious cardiovascular problems.

Mounjaro works by mimicking the effects of two incretins called GIP and GLP-1. So, this medication lowers blood sugar by increasing the amount of insulin released after you eat, making your body more sensitive to insulin (FDA, 2022). 

Additionally, tirzepatide prevents your liver from making additional sugar. It also slows down the time it takes to move food from your stomach to your intestines. This helps you feel fuller longer, which often leads to weight loss, though this is an off-label use of the drug (FDA, 2022; Min, 2021). In a clinical trial, people with type 2 diabetes who took tirzepatide experienced a reduction in body weight of approximately 16 to 28 pounds after one year of treatment (Ludvik, 2021).  

The FDA approves Mounjaro, along with diet and exercise, for controlling blood sugar in adults with type 2 diabetes mellitus. This medication is not intended for people with type 1 diabetes (FDA, 2022).

The FDA may consider approving this medication for the treatment of obesity in the near future, but it isn’t approved for weight loss at this time. In a recent clinical trial, adults with obesity who took tirzepatide had significant weight loss—and maintained it for up to 72 weeks (Jastreboff, 2022).

Talk to a healthcare provider if you’re interested in learning more about tirzepatide for weight loss in patients with or without diabetes.

The most common side effects of Mounjaro are related to the digestive system, such as:

• Nausea/vomiting

• Diarrhea

• Not feeling hungry

• Constipation

• Heartburn

• Pain in your abdomen

• Injection site discomfort or irritation

These side effects are usually mild and often go away with time (Ludvik, 2021). But, if they feel severe or aren’t improving, tell your healthcare provider.

Rarely, serious side effects may occur with Mounjaro. Seek immediate medical care if you think you’re having a severe adverse reaction. Potentially serious side effects, along with symptoms to watch for, may include:

• Pancreatitis (inflammation of the pancreas): Watch for vomiting and intense abdominal pain that might radiate to your back.

• Hypoglycemia (low blood sugar): Watch for symptoms of low blood sugar, like headache, feeling dizzy or irritable, weakness, or sweating. Your healthcare provider will tell you, in advance, what to do at the first sign of these symptoms. For example, they may tell you to drink orange juice or eat hard candy, then check your blood sugar.

• Temporary worsening of an eye problem called diabetic retinopathy: Watch for any changes in your vision.

• Gallbladder problems, such as gallstones: Watch for stomach pain, fever, or vomiting.

• Allergic reactions: Watch for hives, trouble breathing, or swelling of the face, lips, or tongue.

Additionally, you should be aware that severe stomach upset, such as diarrhea and vomiting, can lead to dehydration, which may cause sudden kidney problems. If you experience these symptoms, be sure to stay hydrated. 

Your healthcare provider will show you or your caregiver how to give injections of Mounjaro. It’s given under the skin (a subcutaneous injection) of your thigh, abdomen, or upper arm. Each Mounjaro pen contains one dose (FDA, 2022). 

The typical starting dosage is 2.5 milligrams (mg), given once per week. After 4 weeks, your healthcare provider will likely increase the dose to 5 mg. After another 4 weeks, they may increase your dose again, depending on your blood sugar levels. Mounjaro comes in additional strengths of 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg (the maximum dose).

Mounjaro is typically taken once per week. For example, you may decide to take it every Monday. If you want to change which day of the week you use it, you can simply take Mounjaro on the new preferred day, as long as there are at least three days (72 hours) between doses.

Like most diabetes medications, tirzepatide carries risks, some of which may affect some people more than others. Before prescribing Mounjaro, your healthcare provider will discuss the following warnings with you.

In preclinical studies, tirzepatide caused thyroid cancer in rats. It isn’t known if this risk translates to humans. As a precaution, this medication is not recommended for people with a history of thyroid cancer or a condition called multiple endocrine neoplasia syndrome type 2 (MEN 2). It’s also important to tell your provider right away if you notice possible symptoms of thyroid cancer after starting Mounjaro treatment, such as a lump or growth on your neck, voice hoarseness, or trouble with swallowing or breathing (FDA, 2022).

Additionally, people with the following conditions may need to be monitored very closely if they take tirzepatide:

• Pancreatitis

• Kidney problems

• Diabetic retinopathy

Your healthcare provider will most likely not prescribe Mounjaro for you if you’re pregnant or breastfeeding since it hasn’t been studied in these groups.

Mounjaro may interact with the following types of medications (FDA, 2022): 

• Birth control pills may lose effectiveness if taken with Mounjaro, especially during the initial phase of treatment. This is because Mounjaro affects gastric emptying, which is the rate at which stomach contents move through the digestive tract. The result is that birth control pills could be less effective. So, providers typically recommend an alternative birth control method (such as condoms) during the first 4 weeks of treatment and for 4 weeks after each dose increase.

• Certain antidiabetic medications can raise your risk for low blood sugar, a potential side effect of Mounjaro. These medications include insulins (such as insulin glargine or insulin degludec) and sulfonylureas (such as glimepiride or glyburide).

Other drug interactions are possible. To be safe, tell your healthcare provider and pharmacists about everything you take.

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Current version

July 14, 2022

Written by

Patricia Weiser, PharmD

Fact checked by

Chimene Richa, MD

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About the medical reviewer

Chimene Richa, MD

Dr. Richa is a board-certified Ophthalmologist and medical writer for Ro.