Tirzepatide.

Keep product and jurisdiction attached

In the United States, Mounjaro is labelled as an adjunct to diet and exercise to improve blood glucose control in adults and children aged 10 years and older with type 2 diabetes. Its August 2026 U.S. label also includes reducing the risk of major adverse cardiovascular events in adults with type 2 diabetes at high risk for those events. Zepbound is labelled for chronic weight management in adults with obesity or overweight plus a weight-related condition, and for moderate-to-severe obstructive sleep apnoea in adults with obesity, alongside a reduced-calorie diet and increased activity. The FDA labels contain the actual indications, limitations, contraindications and warnings. The European Union uses Mounjaro with its own product information and conditions. A US label, an EU authorisation and a trial protocol are related records, not interchangeable evidence. For storage instructions that distinguish US Mounjaro and Zepbound presentations, see the tirzepatide storage guide; check the current label for your own product and country. For the distinction between lean tissue and strength, see weight-loss medicines and muscle.

To understand why “fat burning”, appetite and body-weight claims can mean different things, see the guide to weight-loss peptides and fat.

For a closer look at weight, fat and lean mass, see the SURMOUNT-1 body-scan substudy.

The August 2026 US Zepbound label says use with another tirzepatide-containing product or a GLP-1 receptor agonist is not recommended. Tell the prescriber about all weight-management or diabetes medicines you use, including products with different brand names; do not combine or change prescribed treatments on your own.1384

How the dual-target rationale fits together

GIP and GLP-1 are signals from the gut. They act on receptors on cells involved in blood-sugar control and other body processes. Tirzepatide activates both receptor systems.

This description helps explain what researchers are studying. It does not tell us how well the medicine works for a particular person, prove that one simple pathway causes every effect or rank it against other treatments. Trials are needed to measure benefits and harms in the people and settings being studied.16

What SURPASS-2 actually compared

SURPASS-2 was a 40-week trial involving 1,879 people with type 2 diabetes whose blood sugar was not adequately controlled with metformin. Participants were randomly assigned tirzepatide at one of three doses or semaglutide at 1 mg. They and their clinicians knew which treatment they received.

The main outcome was change in HbA1c, a measure of average blood sugar over time. Each tirzepatide group had a greater average reduction than the semaglutide 1-mg group in this trial. This compares particular doses, people and a 40-week period; it does not rank every product or predict an individual result. The trial does not answer every question about long-term complications or people who were excluded.

Eli Lilly, the developer of tirzepatide, funded the trial. The sponsor’s analysis plan addressed outcomes in different ways depending on treatment stopping or additional therapy, and required assumptions for missing results. It did not generally have enough planned statistical power to compare the tirzepatide dose groups.61012

What SURMOUNT-1 actually compared

SURMOUNT-1 was a 72-week trial of 2,539 adults with obesity, or overweight with a weight-related complication. People with diabetes were excluded at the start. Participants were randomly assigned one of three tirzepatide doses or a placebo, alongside lifestyle support. Neither participants nor the study team knew which treatment was assigned.

The two main outcomes were percentage weight change and the proportion of people who lost at least 5% of their starting weight. Average weight loss was greater in the tirzepatide groups than in the placebo group. Overall, 86.0% completed the main treatment period, and more people stopped because of adverse events in the tirzepatide groups than in the placebo group. These results apply to the people and follow-up studied.

Eli Lilly funded the trial. Its analysis plan defined different questions about outcomes after stopping treatment or starting other weight-management interventions. Both approaches require attention to missing data and withdrawals.71113

Does weight loss include muscle?

Weight loss can include fat and lean tissue. On a body scan, lean tissue includes muscle, but also organs and water. It is not a direct measure of muscle strength.

A SURMOUNT-1 scan substudy enrolled 255 people; 160 had both starting and later scans for analysis. After up to 72 weeks, estimated lean mass had fallen by an average 10.9% of its starting amount across the tirzepatide doses and 2.6% with placebo. Fat mass also fell in both groups. These percentages describe changes within each tissue type, not the share of weight lost that was muscle. The scans cannot tell an individual whether their strength or function changed.

Eli Lilly funded the study and took part in its design and analysis. Discuss concerns about strength, nutrition or unintentional weight loss with a clinician. See also the evidence on protein and training.15

What happened after stopping in SURMOUNT-4?

SURMOUNT-4 enrolled 783 adults with obesity or overweight and a weight-related condition, without diabetes, into 36 weeks of tirzepatide plus lifestyle support. Of those, 670 completed the initial period and were randomly assigned to continue tirzepatide or switch to placebo for another 52 weeks. From the weight at randomization—not their original weight—the placebo group gained an average 14.0%, while the continuing group lost a further 5.5%. At week 88, the placebo group remained about 9.9% below its starting weight on average. These are group averages, not a prediction for an individual. During the initial period, 7.0% of those enrolled stopped treatment because of adverse events, mainly gastrointestinal; the randomized phase therefore describes people who continued through that initial period. Results cannot establish what happens after every stopping strategy or in people with diabetes. The manufacturer, Eli Lilly, funded the trial. Do not change prescribed treatment without discussing the reason and alternatives with your prescriber. Explore what happens after stopping and how to read the withdrawal trials.

If weight loss has slowed, see what a plateau can mean and what the studies measured.14

Benefits, harms and treatment burden belong together

Gastrointestinal adverse effects, including nausea, diarrhoea and vomiting, were common in clinical trials and often occurred during dose escalation. The August 2026 US Zepbound label also lists severe gastrointestinal reactions, acute kidney injury due to volume depletion, gallbladder disease, pancreatitis, hypersensitivity, hypoglycaemia with certain other medicines, diabetic-retinopathy complications in people with type 2 diabetes and pulmonary-aspiration precautions. The label says Zepbound is not recommended for people with severe gastroparesis, a condition in which stomach emptying is delayed; discuss any history of this condition with the prescriber. The Zepbound label says low blood sugar can occur and the risk increases with insulin or medicines that stimulate insulin release, such as sulfonylureas. It advises patients to learn the signs of low blood sugar and, for people with diabetes, recommends glucose monitoring before and during treatment. The prescriber may need to adjust the other medicine; do not change a prescribed dose yourself. A warning does not mean every person will experience the event; product information and the evidence supporting each warning differ.4

The August 2026 US Zepbound patient guide says to stop using Zepbound and get medical help immediately for signs of a serious allergic reaction, such as swelling of the face, lips, tongue or throat, or trouble breathing or swallowing. Breathing or swallowing difficulty or a suspected severe allergic reaction is an emergency: call local emergency services. Seek prompt medical advice for other concerning symptoms and check the current instructions for your product.45

The US Zepbound label has a boxed warning about thyroid C-cell tumours: tirzepatide caused these tumours in rats, but whether it causes them in humans is unknown. The label says Zepbound must not be used by people with a personal or family history of medullary thyroid carcinoma, or with multiple endocrine neoplasia type 2 (MEN 2). It is also contraindicated for someone with a known serious allergic reaction to tirzepatide or a Zepbound ingredient. This refers to the named US product; discuss personal and family history and the exact product with the prescriber.4

In January 2026, FDA said its review found no increased risk of suicidal thoughts or behaviour with GLP-1 receptor agonists and requested removal of the relevant warning from Zepbound and two other named weight-management labels. The August 2026 Zepbound label’s recent-changes table records that warning as removed in February 2026. That label change addresses a specific safety question; it does not imply that Zepbound has no other risks, and other jurisdictions and products have their own current information. A fair profile reports denominators, treatment duration, background therapy, withdrawals and how adverse events were collected. If you have a procedure planned, see GLP-1 medicines and anaesthesia.94

Read the evidence on hair loss and weight-loss medicines, including trial rates and possible causes.

See gallbladder risks, trial figures and when to seek care.

See what to check after a missed dose or longer break. For urgent symptoms and the separate evidence on pancreas inflammation, see GLP-1 medicines and pancreatitis.

For practical questions about appetite, meals and nausea with these medicines, see eating and drinking with semaglutide or tirzepatide.

Does tirzepatide affect the contraceptive pill?

Tirzepatide slows stomach emptying and can change absorption of medicines taken by mouth, including an oral contraceptive studied in a product-information trial. Guidance differs between authorities. The US Zepbound label advises people using oral hormonal contraception to switch to a non-oral method or add a barrier method for four weeks after starting treatment and after each dose increase. UK MHRA guidance gives a similar precaution for Mounjaro. EU Mounjaro product information reports reduced hormone exposure after a single tirzepatide dose but considers that observed change not clinically relevant and says no oral-contraceptive dose adjustment is required. These are different regulatory assessments; the blood-level study did not directly measure pregnancy rates. Check the current information for the exact product and country, and discuss contraception, vomiting or diarrhoea, and any concern about pregnancy protection promptly with a prescriber or pharmacist. Do not change prescribed treatment without individual advice. For pregnancy planning, unexpected exposure and breastfeeding, see GLP-1 medicines and pregnancy. See weight medicines and the contraceptive pill for a detailed comparison.161718

How did tirzepatide compare with semaglutide for weight?

SURMOUNT-5 directly compared the two injectable medicines in 751 adults with obesity or overweight with a related condition, without diabetes. Participants were randomly assigned the maximum tolerated dose specified by the study for either medicine for 72 weeks. Estimated average weight change from baseline was −20.2% with tirzepatide and −13.7% with semaglutide, a difference of 6.5 percentage points in that analysis. Gastrointestinal effects were the most common adverse events in both groups. Participants and clinicians knew which treatment was given; the trial was funded by tirzepatide manufacturer Eli Lilly. It compared specific doses and a selected population, not every product, person or health outcome. Weight change alone does not establish which medicine is suitable for someone; discuss benefits, risks and alternatives with a clinician. Read the semaglutide profile for its product and cardiovascular evidence.

Adverse events led 23 of 374 participants assigned tirzepatide (6.1%) and 30 of 376 assigned semaglutide (8.0%) to stop the trial treatment. Gastrointestinal events were the reason for 10 (2.7%) and 21 (5.6%), respectively; these are subsets of the total, not additional people. Stopping treatment was not the same as leaving the study, and the main weight analysis was designed to account for treatment discontinuation. These figures describe this open-label trial and do not establish an individual’s risk or a definitive safety ranking.19

Why comparisons can mislead

Two studies may both report changes in weight or HbA1c, but differ in who took part, starting measurements, treatment doses, comparison groups, other medicines and length of follow-up. Researchers may also analyse results differently.

A trial against placebo answers a different question from a trial against semaglutide or another treatment. Putting the largest number from each study side by side does not control for these differences. Keep sponsor announcements separate from full study reports and regulator decisions.672

Five questions for a tirzepatide claim

Which product and country does the claim refer to? Who was studied, and did they have diabetes or obesity? What was the treatment compared with, what other treatment did people receive, and how long were they followed? How many people had benefits or harms, and how many stopped treatment? Is the source describing a proposed mechanism, a published trial, a regulator decision or a sponsor announcement?

For a current US claim, check that the cited Mounjaro or Zepbound label matches the date and approved use being discussed.842

Development & regulatory context

These selected records are not a complete global legal-status list. Approval depends on the product, use, population and country; check each record’s date.