Is Mounjaro Safe for Weight Loss?

Mounjaro (tirzepatide) is an injectable prescription medication that helps adults with Type 2 diabetes manage blood sugar. The drug is made and distributed by Eli Lilly and Company.

Mounjaro belongs to a class of medications known as GLP-1 receptor agonists. It focuses on the body’s receptors for GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1).

In April 2023, The New York Times reported a major increase in people using Mounjaro off-label for weight loss. The article suggested Mounjaro may be more effective for weight control than Ozempic®, another
 GLP-1 RA diabetes drug used off-label for weight loss.

Although doctors can prescribe Mounjaro off-label for weight loss, this use is not approved. The FDA has only approved Mounjaro to treat Type 2 diabetes. 

Research shows that Mounjaro can be effective for weight loss. Mounjaro stimulates hormones that manage blood sugar and decrease appetite to stimulate weight loss. Essentially, it can make people feel fuller faster, effectively managing diabetes and obesity.

Multiple studies looking into Mounjaro and its active ingredient, tirzepatide, have seen promising results for diabetes and weight loss. Here are some examples: 

• 40-week trial: A 2021 study of 1,879 patients compared Mounjaro and Ozempic for treating Type 2 diabetes. Although the study wasn’t intended to examine weight loss, the researchers found that those who took Mounjaro lost more weight.
• 72-week clinical trial: A 2022 controlled study of more than 2,500 adults taking weekly dosages of 5 mg, 10 mg and 15 mg of tirzepatide lost an average of 15% of their body weight. Approximately 85% of the participants taking 5 mg of tirzepatide experienced weight loss of 5% or more. Some participants receiving 10 and 15 mg dosages reduced their weight by as much as 20%.
• JAMA study: A 2024 JAMA investigation compared the weight loss of obese adults taking tirzepatide with those using semaglutide. The researchers concluded that tirzepatide led to substantially more weight loss than semaglutide, the active ingredient in Ozempic.

Because of these and similar findings, doctors are prescribing Mounjaro to obese people to help them lose weight, whether or not they have diabetes. 

However, medications like Mounjaro often require long-term use. Those who discontinue them risk regaining the weight they lost. A 2022 study found that participants taking drugs like Mounjaro regained about two-thirds of the weight they lost one year after stopping the medication.

Mounjaro risks and side effects

Although it can be effective for weight loss, Mounjaro poses side effects and risks. Some common side effects of Mounjaro include:

• Constipation
• Diarrhea
• Loss of appetite
• Nausea
• Stomach pain
• Upset stomach
• Vomiting

Mounjaro may also cause severe side effects, such as:

• Allergic reactions: Breathing problems, difficulty swallowing, dizziness, fever, hives, joint pain, nausea, rapid heartbeat, stomach cramps, swollen lymph nodes, swelling of the face, lips, mouth, throat or tongue, vomiting and wheezing.
• Cholelithiasis: Gallbladder issues, such as fever, pale-colored stool, stomach pain and yellow-tinted eyes or skin.
• Gastroparesis: Mounjaro use has been linked to gastroparesis (delayed gastric emptying). Gastroparesis delays or impedes the movement of food from the stomach to the small intestine, even though no blockage in the stomach or intestines exists. 
• Hypoglycemia: Mounjaro may lower blood sugar, leading to accelerated heartbeat, anxiety, blurred vision, confusion, dizziness, headaches, hunger, slurred speech, sweating, shakiness and seizures.
• Kidney damage: Mounjaro can lead to kidney damage in those who are dehydrated while taking the drug. Symptoms of kidney damage include chest pain or pressure, confusion, foot, ankle or leg swelling, lessened need to urinate, nausea, seizures, unusual fatigue and weakness. 
• Pancreatitis: Mounjaro can inflame the pancreas. Symptoms include vomiting or severe pain in the upper region of the abdomen that travels to the back.
• Stomach issues: Serious stomach problems, including severe diarrhea, nausea or vomiting.
• Thyroid tumors: Mounjaro use may lead to the development of thyroid tumors, which can be cancerous. Some symptoms of thyroid tumors include hoarseness, a lump or swelling of the neck, problems swallowing or trouble breathing.
• Vision problems: Those with diabetic retinopathy may experience new or worsening vision issues with Mounjaro, such as black spots, blurred vision, central vision loss, floaters or the inability to see colors. 

Call your healthcare provider immediately if you are taking Mounjaro and experiencing any of these symptoms.

People injured by Mounjaro are filing lawsuits against the drug company Eli Lilly. The lawsuits allege that Eli Lilly failed to warn users about serious risks associated with taking Mounjaro, particularly those connected with off-label use. 

The diabetes lawsuits concerning Mounjaro and other GLP-1 receptor agonists (Ozempic, Rybelsus®, Trulicity®, Wegovy®, Zepbound®) have been consolidated into multidistrict litigation (MDL) 3094 in the U.S. District Court for the Eastern District of Pennsylvania under Judge Mitchell S. Goldberg. As of February 2025, there were 1,443 cases pending in MDL 3094. 

No — Mounjaro is not FDA-approved for weight loss, although approval is expected. Instead, the medication is approved to treat adults with Type 2 diabetes. Zebound, another medication containing tirzepatide, is explicitly approved for weight loss.

Medical professionals consider Mounjaro effective for weight loss. Research has found that taking Mounjaro, along with eating a balanced diet and exercising, may encourage people to lose weight. 

However, research is ongoing regarding whether Mounjaro must be used long term to maintain weight loss.

Is Mounjaro safe for off-label uses?

The safety of Mounjaro for off-label uses is still being reviewed. However, prescribing medications off-label is very common. The FDA supports the use of medications for off-label purposes, such as using Type 2 diabetes drugs to treat obesity, when medically suitable. 

However, Mounjaro has been associated with serious side effects, including gastrointestinal issues. Consult a medical professional who knows your health background before taking a drug for off-label use. 

Is Mounjaro safe for weight loss?

Although effective for weight loss, the risks posed by Mounjaro may not be worth the benefits of the drug. Many of the unlisted adverse side effects of Mounjaro and other GLP-1 RA drugs can be life-altering or life-threatening.

Our medical attorneys have advocated for thousands of patients seriously hurt by dangerous prescription and over-the-counter drugs like Mounjaro. If you believe a medication made you sick or harmed you, our attorneys have the resources needed to thoroughly investigate your potential claim.

Read more on our medical drug litigation experience.

Do not stop taking a prescribed medication without first consulting with your doctor. Discontinuing a prescribed medication without your doctor's advice can result in injury or death. Mounjaro, Ozempic, Rybelsus, Trulicity, Wegovy and Zepbound remain approved by the U.S. Food and Drug Administration.