Mounjaro and weight loss

What sources report

Mounjaro weight loss figures come from trials that were built to test blood sugar control. Every trial on the US label enrolled people with type 2 diabetes, and body weight was one of the outcomes measured along the way.¹ The approved uses are blood sugar control and lowering heart risk, both in type 2 diabetes.¹

Weight in the diabetes trials

Where the label gives a range, it spans the doses tested in that trial (5 to 15 mg once weekly in adults).¹

Three patterns run through the table. Weight fell in every Mounjaro group, including in SURPASS-5, where everyone was also using insulin.¹ In every adult trial the average loss grew with the dose, for example from 7.6 kg on 5 mg to 11.2 kg on 15 mg in SURPASS-2; in children, BMI fell 6.9% on 5 mg and 10.8% on 10 mg.¹ Where the comparison was daily insulin, the insulin groups gained 1.7 to 1.9 kg while the Mounjaro groups lost weight.¹

Why weight changes

The labels tie the change to appetite and digestion. Tirzepatide lowers calorie intake, an effect the Zepbound label says is likely mediated through appetite.⁸ Both of its target receptors are found in parts of the brain involved in appetite, and animal studies show tirzepatide reaching and switching on neurons in the regions that regulate food intake.⁷ It also slows stomach emptying, most of all after the first dose.¹

On the Mounjaro label, lower appetite shows up as a side effect: decreased appetite was reported by 5% to 11% of adults on 5 to 15 mg, against 1% on placebo.¹ The weight lost is more fat mass than lean mass, which means some lean mass is lost as well.⁸

The tirzepatide brand approved for weight

FDA approved Zepbound (tirzepatide) for chronic weight management on November 8, 2023.⁹ Its label covers reducing excess body weight and keeping the reduction long term in adults with obesity, or with overweight plus at least one weight-related condition.⁴ FDA's approval notice defined obesity there as a BMI of 30 or above and overweight as 27 or above, the latter only with a weight-related condition.¹⁰ The same label adds moderate to severe obstructive sleep apnea in adults with obesity.⁵

SURMOUNT-1 tested tirzepatide for weight in adults with obesity, or overweight with a weight-related condition, and no diabetes: 5, 10 or 15 mg or placebo once weekly for 72 weeks, with the doses reached over a 20-week escalation.¹¹ At week 72, the average weight change was -15.0%, -19.5% and -20.9% for the 5, 10 and 15 mg groups, compared with -3.1% for placebo.¹²¹³

Zepbound follows its own schedule, in which 2.5 mg is a starting dose and not a maintenance dose.⁶ Its label also says coadministration with other tirzepatide-containing products, or with any GLP-1 receptor agonist, is not recommended.⁵ More on that brand: What is Zepbound? and Tirzepatide and weight loss.

Outside the United States

Approved uses differ by region. In the European Union, Mounjaro is also used together with diet and physical activity to help adults lose weight and keep their weight under control.¹⁶ There, too, it can only be obtained with a prescription.¹⁷

Unapproved tirzepatide sold for weight loss

FDA's warnings on unapproved GLP-1 drugs cover tirzepatide sold outside an approved product. Compounded versions are not FDA approved, and by May 31, 2026 FDA had more than 730 adverse event reports tied to compounded tirzepatide.³ FDA has warned companies that sold tirzepatide falsely labeled "for research purposes" or "not for human consumption", and it urges consumers not to purchase such products, which it describes as of unknown quality.³ Illegally marketed GLP-1 drugs may be counterfeit, carry wrong or harmful ingredients, or hold too little, too much or no active ingredient.¹⁸ Because FDA describes these products as of unknown quality, the trial results on this page cannot be assumed to apply to them.³

What the label says

• Approved uses: blood sugar control with diet and exercise in type 2 diabetes, for adults and children 10 and older, and lowering the risk of cardiovascular death, heart attack or stroke in high-risk adults with type 2 diabetes. Weight loss is not among them.¹
• Dose steps follow blood sugar: the dose rises by 2.5 mg, after at least 4 weeks on the current dose, only when more glycemic control is needed, up to 15 mg in adults.¹ The label has no weight-based step, and the prescriber sets the dose; see Mounjaro dosage.
• Stomach effects and fluids: most nausea, vomiting and diarrhea occurred while the dose was being raised, and acute kidney injury has been reported mostly in people dehydrated by those effects.¹
• Gallbladder: acute gallbladder disease occurred in 0.6% of people on Mounjaro, against 0% on placebo.¹
• Birth control pills: they may work less well, so the label advises a non-oral method, or an added barrier method, for 4 weeks after starting and for 4 weeks after each dose increase.¹
• Boxed warning: rats given tirzepatide developed thyroid C-cell tumors, and the risk to humans has not been determined. The label rules out Mounjaro for anyone with a personal or family history of medullary thyroid carcinoma or MEN 2.¹

The full list, with rates by dose, is on Mounjaro side effects.

Limits of the evidence

• Who was studied: every trial on the US Mounjaro label enrolled people with type 2 diabetes, so its weight figures describe that group.¹
• How weight was reported: in the sources reviewed here, adult weight results for Mounjaro are given in kilograms at the end of each trial. The SURPASS kilograms and the SURMOUNT-1 percentages come from different groups and units, so they cannot be lined up directly.
• After stopping: the sources reviewed here hold no data on weight after Mounjaro is stopped. In SURMOUNT-4, adults without diabetes who switched from tirzepatide to placebo regained 14.0% of body weight between weeks 36 and 88, while those who stayed on it lost a further 5.5%.¹⁵
• Averages: each figure is a group average under trial conditions, not a forecast for one person.

Read next

The Mounjaro profile covers the medicine in full, and Mounjaro benefits and uses summarizes every trial outcome on the label. Glucose results from the same trials are on Mounjaro and blood sugar, and the two brands are set side by side in Mounjaro vs Wegovy. The wider goal page is Peptides and weight loss.