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Mounjaro for Weight Loss

Although off-label use of Mounjaro indicates its effectiveness for weight loss in overweight individuals or those considered obese, the FDA has yet to formally approve it for the purpose. In clinical trials, participants using Mounjaro achieved an average 26% reduction in body weight in less than two years.

Last Modified: December 13, 2023
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Is Mounjaro FDA-Approved for Weight Loss?

Mounjaro does not have FDA approval as a weight loss drug, making any uses for this purpose an off-label use. The U.S. Food and Drug Administration limits approval for the use of the injections to assist adults diagnosed with Type 2 diabetes with improving control of their blood sugar levels. Mounjaro is under review for approval as a weight loss medication.

“Today, the U.S. Food and Drug Administration approved Mounjaro (tirzepatide) injection to improve blood sugar control in adults with Type 2 diabetes, as an addition to diet and exercise.” — FDA, May 13, 2022”

The FDA approves drugs for use when research indicates the benefits associated with drug use outweigh the possible risks. The approval of Mounjaro came when drug trials showed injections of the drug helped Type 2 diabetes patients lower their A1C levels as both a stand-alone or companion treatment for managing diabetes.

Doctors are able to prescribe Mounjaro for uses other than diabetes management, but these off-label uses come with both benefits and risks. It is important to remember that there is no determination of safety by the FDA if you and your healthcare provider decide to use a medication for off-label use.

Eli Lilly Seeking FDA Approval of Mounjaro for Weight Loss

Eli Lilly, the pharmaceutical company manufacturing Mounjaro, is seeking FDA approval for the tirzepatide injections as a weight loss treatment after conducting clinical trials to this end. The clinical trials involved individuals diagnosed with obesity or who were overweight with weight-related comorbidities and Mounjaro injections in conjunction with lifestyle interventions.

Fast Track Approval
  • During phase 3 of the drug trial, the results from using Mounjaro for weight loss averaged reductions of over 60 pounds per participant over approximately 19 months.
  • The requested approval for the use of Mounjaro for weight loss is still under FDA review, although the initial FDA Fast Track designation occurred in October 2022.
  • Eli Lilly received approval for rolling submissions, allowing the company to continually submit completed components of the application rather than waiting until the trial and full study are complete.

Fast Track approval with the FDA attempts to safely bring a drug to the market to meet an unmet medical need. The goal is to speed up the development and review of a product designed to treat serious medical conditions. With a Fast Track, there must be no other alternative drug on the market for the condition or it must show superior effectiveness.

A Fast Track designation occurs at the request of the drug company, and if accepted, the company receives more frequent communication with the FDA, as well as accelerated or rolling review and approval.

In November 2023, the FDA approved the drug Zepbound for chronic weight management in obese and overweight adults. Zepbound, also manufactured by Eli Lilly, shares the same active ingredient as Mounjaro (tirzepatide) but is specifically for weight loss patients.
Source: FDA.gov

How Effective Is Mounjaro for Weight Loss?

Clinical trials showed Mounjaro has some effectiveness as a weight loss drug since its users achieved a total mean weight loss of 26.6% over 84 weeks. Participants entered the Eli Lilly study with an average body weight of 241.4 lbs. Over the course of the study, they reduced both their weight and waist circumference size with the injections and corresponding lifestyle changes.

Weight Loss Effectiveness
  • Phase 3 of the clinical trial of Mounjaro revealed the potential impact on weight loss.
  • In this trial, individuals who were both overweight and had Type 2 diabetes experienced 15.7% weight loss.
  • Of the 800 participants in the clinical trial concerning FDA Fast Track approval, 580 lost 5% of their body weight in 12 weeks.
  • After 84 weeks of using Mounjaro, participants lost a significant amount of weight compared to those in the trial taking a placebo, highlighting the superiority of the drug.

Researchers credit Mounjaro’s ability to address the body’s appetite center in the brain as the reason for its impressive results compared to other medications and supplements on the market for weight loss. Ozempic (semaglutide), another diabetes management drug, is also receiving off-label use for weight loss. When comparing Mounjaro vs. Ozempic, neither has FDA approval for weight loss use. However, Wegovy, a larger dose of semaglutide than Ozempic, and Zepbound, another tirzepatide drug, do have FDA approval for weight loss.

How Long Does It Take to Lose Weight Using Mounjaro?

Mounjaro users can expect to lose weight over a period of weeks, with trials showing positive results as early as 12 weeks. In the Eli Lilly-funded study where participants averaged 26.6% weight loss, that reduction took 72 weeks. In each Eli Lilly study, the effectiveness of the drug increased with substantial lifestyle changes.

In a presentation at the Annual Meeting of the European Association for the Study of Diabetes, a meta-analysis of studies involving data taken from 18,472 patients with Type 2 diabetes showed Mounjaro’s effectiveness in weight loss over semaglutide options in as little as 12 weeks. Higher doses of tirzepatide showed higher amounts of weight loss

Side Effects of Mounjaro

Some users experience side effects of Mounjaro, with the most common being gastrointestinal concerns.

Possible Mounjaro Side Effects
  • Acute gallbladder disease
  • Acute kidney injury
  • Constipation
  • Decreased appetite
  • Diabetic retinopathy
  • Diarrhea
  • Dyspepsia
  • Gastroparesis
  • Hypersensitivity reactions
  • Hypoglycemia
  • Nausea
  • Pancreatitis
  • Persistent stomach pain
  • Upset stomach
  • Thyroid tumors
  • Vomiting

Mounjaro has a boxed warning for thyroid C-cell tumors, particularly with those having either a personal or family history of thyroid cancer or multiple endocrine neoplasia syndrome. The FDA uses this safety-related warning to call consumer attention to the serious risks of taking a particular drug.

Eli Lilly is facing legal action over allegations that Mounjaro harmed patients. Plaintiffs in the Mounjaro lawsuits argue that drug-induced stomach paralysis and severe vomiting left permanent damage. Ozempic users cite similar claims of severe gastrointestinal injuries.

Should I Take Mounjaro To Lose Weight?

Taking Mounjaro to lose weight is a personal decision that should involve the insight and advice of your primary care physician. Because of the potential for adverse side effects or risks associated with off-label use of a drug, you should only use Mounjaro off-label under the supervised use of your physician.

Though the FDA is currently evaluating the safe use of Mounjaro for weight loss, it does not currently have approval for this purpose. The potential risks of using the drug off-label may outweigh the benefits in your particular situation.

Please seek the advice of a medical professional before making health care decisions.