Mounjaro (Tirzepatide)

Mounjaro (tirzepatide) is a medication that the U.S. Food and Drug Administration (FDA) approved in 2022 to help adults with type 2 diabetes manage their blood sugar levels. It works best when combined with a balanced diet and regular physical activity.

It comes in single-dose, pre-filled injection pens, as well as single-dose vials. Your health care provider will teach you how to inject Mounjaro correctly.

Serious Mounjaro side effects include gastroparesis (stomach paralysis) and other gastrointestinal problems. Hundreds of lawsuits focus on injuries from these severe side effects.

Its label contains a black box warning — the FDA’s most serious. It says Mounjaro may raise the risk of a rare type of thyroid cancer, based on animal studies. People with certain thyroid conditions should not use it. Talk to your doctor about any neck lumps, difficulty breathing, trouble swallowing or hoarseness while taking Mounjaro.

Mounjaro not only aids in managing blood sugar but can potentially assist with weight loss. By controlling how quickly we digest food and how full we feel, Mounjaro helps maintain stable blood sugar levels and might lead to weight loss.

How Does Mounjaro Compare to Ozempic and Wegovy?

Mounjaro targets blood sugar differently than popular semaglutide drugs like Ozempic and Wegovy. Mounjaro activates both GLP-1 and GIP receptors, which affect blood sugar. Ozempic and Wegovy activate only GLP-1 receptors.

A 2021 clinical trial called SURPASS compared Mounjaro to Ozempic and Wegovy. The trial’s results, published in the New England Journal of Medicine, found that Mounjaro is more effective in lowering blood sugar and aiding weight loss.

In 2023, the FDA approved a similar tirzepatide medication called Zepbound for managing weight in adults with obesity or related health issues. However, Mounjaro itself is not FDA-approved for weight loss.

The most frequently reported side effects of Mounjaro are gastrointestinal. They typically happen when you first start taking the medication or increase your dosage. These side effects usually ease over time.

These most common side effects were reported in 5% or more of people who participated in Mounjaro clinical trials. They are usually mild to moderate, often diminish over time and are more likely to occur when increasing doses.

While most side effects of Mounjaro are mild, there are some serious risks.

If you’re taking Mounjaro, be aware of these risks and consult a health care provider with any concerns.

Mounjaro and Gastroparesis

Some people using Mounjaro have reported stomach issues like nausea and vomiting, with a few experiencing gastroparesis, or stomach paralysis. It’s a condition where food moves very slowly or stops in the stomach.

Gastroparesis is a serious health issue that can lead to problems like malnutrition, dehydration, infections and unstable blood sugar levels.

These cases are rare. Gastroparesis did not show up in clinical trials for Mounjaro, and the FDA doesn’t list it as a side effect. Doctors also note that diabetes patients can develop gastroparesis on their own, making it hard to know if the drug is the cause.

However, some Mounjaro lawsuits have claimed the medication is to blame for gastroparesis.

What To Do if You’ve Experienced Mounjaro Side Effects

If you’re taking Mounjaro and notice any side effects, don’t stop taking it by yourself. It’s important to talk to your doctor first. They can help decide the best course of action, whether it’s adjusting your dose or creating a plan to stop the medication safely.

If you experience serious symptoms like persistent stomach pain, vomiting, swelling in your face or throat, trouble breathing or itchy rashes or hives, seek medical help immediately. These could be signs of serious conditions, such as pancreatitis, gallbladder issues or an allergic reaction.

You can also report any side effects to the FDA by visiting its MedWatch website.

If you suffered severe gastrointestinal injuries that you believe were caused by Mounjaro, you may be able to file a Mounjaro lawsuit. Drugwatch has vetted leading national law firms involved in GLP-1 litigation. We can help you find the right attorney for your situation.

A federal panel combined 55 GLP-1 lawsuits into a multidistrict litigation (MDL) in February 2024. An MDL combines several similar lawsuits in a single district court to expedite the legal process.

As of July 2025, there were 1,997 cases pending in an MDL in the U.S. District Court for the Eastern District of Pennsylvania. Mounjaro’s manufacturer, Eli Lilly and Company, is a defendant in the MDL.

The lawsuits claim people suffered gastrointestinal injuries after taking Mounjaro, Ozempic, Rybelsus, Trulicity or Wegovy. These medications all utilize GLP-1 RAs (glucagon-like peptide-1 receptor agonists) as active ingredients.

Mounjaro received FDA approval in 2022 for Type 2 diabetes. The approval came with standard warnings about gastrointestinal side effects, along with a “black box” warning about the potential risk for thyroid tumors. Since then, the FDA has identified additional serious gastrointestinal complications through its adverse event monitoring system, resulting in periodic updates to the warnings and precautions on Mounjaro’s label.

FDA Warnings Over Unapproved Uses and Compounded Versions

During recent shortages of GLP-1 medications, some pharmacies sold generic, unapproved versions of Mounjaro. However, the FDA does not review these compounded drugs for safety, effectiveness or quality.

Once the shortages ended, the FDA ordered a halt to the sale of compounded versions of Mounjaro in March 2025. However, there are still some workarounds compounders may leverage to keep their products on the market, like changing dosages or adding ingredients.

The FDA is warning patients and health care providers about the risks associated with using unapproved or mixed versions of GLP-1 drugs for weight loss, such as Ozempic and Mounjaro. As of April 2025, the FDA had received 1,000 reports of health issues linked to these unapproved drugs.

The FDA recommends that you only get Mounjaro prescriptions from licensed doctors and fill them at licensed pharmacies.