Mounjaro for Weight Loss: What Its Diabetes Trials Measured, and Why Zepbound Is the Same Drug With a Weight Label

Mounjaro is not approved for weight loss. Both of its indications are for type 2 diabetes. Weight appears in its trials only as a secondary measurement, and the label's own tables put it at 5.6% to 11.9% of body weight over 40 to 52 weeks, depending on the dose and the trial. The same molecule, tirzepatide, has had a separate weight-management approval since November 2023 under a different name: Zepbound. This page sets out what Mounjaro's own record shows, and what prescribing it "off-label" for weight means in practice.

Sources were read on 9 October 2026: the Mounjaro prescribing information (Eli Lilly, DailyMed, effective 27 August 2026), the Zepbound prescribing information (effective 28 August 2026), FDA's approval records and Lilly's Mounjaro savings terms. This page reports the trials; it does not suggest a drug or a dose for anyone.

What the Mounjaro label approves

Section 1 of the label lists two uses:

Mounjaro was first approved on 13 May 2022 (Drugs@FDA, NDA 215866). The cardiovascular indication rests on an outcomes trial of 13,299 adults (SURPASS-CVOT, NCT04255433) against dulaglutide, the drug in Trulicity. The label's pharmacology section says tirzepatide "reduces body weight in patients with type 2 diabetes mellitus" — a description of what the drug does, not an approved purpose.

What Mounjaro's own trials measured on weight

All five adult glycaemic-control trials in section 14 report mean body-weight change as a secondary result, at three maintenance doses. The label prints starting weight and change in kilograms; the percentages below are glp1ledger's arithmetic from those two figures, which the label does not print. Kilograms are converted at 2.2046 lb.

Mean starting weights ran from 84.5 kg to 96.0 kg. Three things in this table are easy to miss:

• The comparator matters more than it looks. In SURPASS-3 and SURPASS-4, people on insulin gained weight, so the label's "difference from comparator" at 15 mg (-13.2 kg and -12.2 kg) is larger than anything anyone lost on Mounjaro. A figure quoted as "13 kg more than insulin" is not a 13 kg loss.
• Insulin users lost the least. SURPASS-5, where everyone was already on basal insulin, has the smallest losses at every dose — 9.2% at 15 mg — and its placebo arm gained 1.6 kg.
• There is a dose gradient in every trial. Weight change grows from 5 mg to 15 mg in all five, unlike Ozempic's 2 mg versus 1 mg comparison, where the label calls the weight difference not significant (see Ozempic for weight loss).

SURPASS-2 is also the only trial in either label that puts tirzepatide directly against semaglutide at a diabetes dose; Mounjaro vs Ozempic sets that trial out in full.

Why a second application exists: Zepbound

On 8 November 2023 FDA approved tirzepatide for chronic weight management as Zepbound, noting in its announcement that the active ingredient was "already approved under the trade name Mounjaro". The weight indication came from trials designed around weight: 72 weeks long, in people with obesity or overweight, with weight as the primary outcome.

Zepbound's label carries one trial in the population Mounjaro is approved for. In SURMOUNT-2 (Study 2, 938 adults with type 2 diabetes), mean weight change at 72 weeks was -14.7% on 15 mg and -12.8% on 10 mg, against -3.2% on placebo. That is the closest the labels come to a Mounjaro weight-management figure, and it comes from a longer trial with a different primary outcome. Set against the 20.9% the same dose gave in people without diabetes (SURMOUNT-1), it is the "diabetes discount" that Mounjaro vs Zepbound works through — read that page for the side-by-side; this one does not repeat it.

These are numbers from two programmes, not a head-to-head. No trial randomised people to Mounjaro or Zepbound, and none could: it is the same drug.

What "off-label" means for access

FDA allows a prescriber to write an approved drug for an unapproved use when they judge it medically appropriate, so an off-label Mounjaro prescription is legal. What changes is the paperwork around it:

• The savings card. Lilly's Mounjaro card requires a prescription "for an approved use consistent with FDA approved product labeling" and enrolment in a commercial drug plan; Medicare, Medicaid, TRICARE and other government programmes are excluded (terms read 9 October 2026). A weight-loss prescription without type 2 diabetes is not an approved use. The full terms, including the $499 tier for plans that exclude Mounjaro, are on the Mounjaro savings card page.
• Insurance. Plans that cover Mounjaro commonly attach a prior-authorization requirement confirming type 2 diabetes; how those requests work is on GLP-1 prior authorization, and plan-level coverage on GLP-1 insurance coverage.
• The weight-labelled route. Zepbound has its own self-pay vial and KwikPen prices from Lilly; the dated ladder is on what Zepbound costs.

What happens on stopping

The Mounjaro label does not say. The only stopping data in any tirzepatide label come from Zepbound's withdrawal trial (Study 4, NCT04660643): after 36 weeks on tirzepatide, 670 people were randomised to continue or switch to placebo. Over the following 52 weeks the placebo group regained 14.0% of body weight, while the continuing group lost a further 5.5%. That trial excluded people with type 2 diabetes, so it describes the Zepbound population, not Mounjaro's. The wider record on stopping is on stopping GLP-1 medication.

Safety does not change with the reason for the prescription

The label's warnings apply to every Mounjaro prescription: a boxed warning on thyroid C-cell tumours in rats, and warnings on pancreatitis, gallbladder disease, low blood sugar when combined with insulin or a sulfonylurea, kidney injury from dehydration, severe gastrointestinal adverse reactions, hypersensitivity reactions, diabetic retinopathy complications and pulmonary aspiration under anaesthesia. The safety data were gathered in people with type 2 diabetes. The brand's side-effect rates are on Mounjaro side effects.

What this page cannot tell you

• No trial measured Mounjaro in people without diabetes. Every Mounjaro weight figure above comes from people with type 2 diabetes over 40 to 52 weeks.
• The percentages are derived. They are computed from the label's mean baseline and mean change, not printed by Lilly, and a ratio of two means is not the same as the mean of individual percentage changes.
• No figure here predicts one person's result. Trial means sit inside wide individual spreads, which the Mounjaro label does not print for weight.

Whether Mounjaro, Zepbound or neither is appropriate for someone is a decision for a prescriber who knows their history.

Sources

• MOUNJARO (tirzepatide) prescribing information, Eli Lilly and Company, NDA 215866, DailyMed set ID d2d7da5d-ad07-4228-955f-cf7e355c8cc0, effective 2026-08-27, read 2026-10-09: sections 1, 5, 12.1 and 14 (Tables 4–8). Trial registrations named in the label: NCT03954834, NCT03987919, NCT03882970, NCT03730662, NCT04039503.
• ZEPBOUND (tirzepatide) prescribing information, Eli Lilly and Company, DailyMed set ID 487cd7e7-434c-4925-99fa-aa80b1cc776b, effective 2026-08-28, read 2026-10-09: section 1, Table 2 (Studies 1 and 2) and Table 6 (Study 4, NCT04660643).
• U.S. Food and Drug Administration, "FDA Approves New Medication for Chronic Weight Management", 8 November 2023, fda.gov; Drugs@FDA record for NDA 215866 (original approval 2022-05-13), via openFDA.
• Eli Lilly and Company, "Savings & Coverage | Mounjaro", card eligibility and terms, mounjaro.lilly.com/savings-coverage, read 2026-10-09.