Tirzepatide: Medicine Overview
Tirzepatide acts on both GIP and GLP-1 receptors and is sold as Mounjaro and Zepbound; this overview covers label indications, key trials and safety information from the FDA and EMA.
Content last updated . This page has not been medically reviewed.
What tirzepatide is
Tirzepatide is a once-weekly injectable that activates two gut-hormone receptors, GIP and GLP-1. The US label says it is based on the GIP sequence, contains an unusual amino acid (aminoisobutyric acid) at two positions, and carries a fatty diacid chain that lets it bind albumin and last longer in the body. [1] Its half-life is about 5 days. [1] It is a modified peptide made for medicine, not a hormone your body makes. For the biology, see GLP-1 and GIP biology, and for how it differs from GLP-1-only drugs see GLP-1 vs dual-agonist medicines.What the trials showed
- Weight, no diabetes. In a 72-week trial of 2,539 adults with obesity, or overweight plus a related condition, and without type 2 diabetes, average weight change was -3.1% with placebo versus -15.0%, -19.5% and -20.9% across the three studied maintenance strengths. These are study arms, not guidance. [2]
- Weight, type 2 diabetes. In people with type 2 diabetes the average change was -3.2% with placebo versus -12.8% and -14.7% on the two studied strengths. [2]
- Sleep apnea. In two 52-week trials in adults with obesity and moderate to severe sleep apnea, the apnea-hypopnea index (breathing pauses per hour) fell significantly more than with placebo. [2]
- Heart events versus another drug. SURPASS-CVOT randomized 13,299 people with type 2 diabetes and heart disease to tirzepatide or dulaglutide. Major heart events were 12.1% versus 13.0% (hazard ratio 0.92, interval 0.83 to 1.01). The label says tirzepatide was non-inferior and that superiority was not established. Label: mixed on the question of being better than dulaglutide. [1]
- Children. A 30-week trial in 99 children 10 and older with type 2 diabetes supports that use in the US. [1]
Weight lost in a trial is a measured outcome in people who also got diet and activity counseling. [2] Whether weight loss lasts after stopping is not answered by these label tables; see obesity and weight management evidence.
Care context, off-label and compounded versions
Tirzepatide is prescription-only, and decisions about starting, switching or stopping belong with a prescriber. FDA says unapproved versions of tirzepatide do not receive its review for safety, effectiveness or quality, and it reported fraudulent products labeled as compounded tirzepatide and dosing-error reports. [4] Using an approved drug for a use not on its label is off-label, and FDA has not determined it is safe and effective for that use. [5] See semaglutide vs tirzepatide for a side-by-side comparison, and weight-loss medications and medical care for the wider context.Frequently asked questions
Are Mounjaro and Zepbound the same medicine?
Both contain tirzepatide. In the US they have separate labels: Mounjaro for type 2 diabetes and Zepbound for weight and sleep apnea. [1][2]
Is tirzepatide better than semaglutide?
The labels do not compare them directly. The one head-to-head label trial read here compared tirzepatide with dulaglutide, not semaglutide. [1]
Does tirzepatide affect birth control pills?
The Mounjaro label includes an interaction note for oral hormonal contraceptives; ask a prescriber or pharmacist what applies to you. [1]
Is compounded tirzepatide the same as the approved product?
FDA says compounded drugs are not FDA approved and are not reviewed for safety, effectiveness or quality before marketing. [4]
Where do I report a problem?
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read the evidence labels
Labels used on this page: approved medicine (reviewed by a named regulator for a named use) and mixed where a trial result did not clearly favor the drug. One molecule, two US brands: the label for Mounjaro and the label for Zepbound are separate documents with different indications. [1][2]
Approved uses by brand (read 2026-10-22)
| Brand | US (FDA label) | EU (EMA page) |
|---|---|---|
| Mounjaro | Type 2 diabetes blood sugar control in adults and children 10 and older; fewer major heart events in adults with type 2 diabetes at high risk [1] | Type 2 diabetes in adults, adolescents and children 10 and older, and weight management in adults with obesity, or overweight plus a weight-related condition [3] |
| Zepbound | Weight reduction and long-term maintenance in adults with obesity, or overweight plus a weight-related condition; moderate to severe obstructive sleep apnea in adults with obesity [2] | Not verified (no separate EMA page for this brand was read); the Mounjaro page itself carries the weight indication [3] |
The EMA page also points to trial results in sleep apnea and heart failure with preserved ejection fraction, which are described in the product information but are not listed as separate indications. [3] Both US labels say tirzepatide should not be combined with other tirzepatide products or any GLP-1 receptor agonist. [2]
The labels list injectable pens, single-dose vials, multi-dose vials and a multi-use pen as forms, and note that products differ in how many doses each holds. [1] That is one reason a "vial of tirzepatide" from a non-approved source is not the same as an approved product; see compounded and unapproved GLP-1 products.
Main safety information from the labels
- Boxed warning. In rats tirzepatide caused thyroid C-cell tumors; human relevance is unknown. It is contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2. [2]
- Common effects. For Zepbound, 5% or more of people had nausea, diarrhea, vomiting, constipation, abdominal pain, dyspepsia, injection site reactions, fatigue, allergic-type reactions, belching, hair loss or reflux. [2]
- Serious warnings. Severe stomach and bowel reactions (not recommended with severe gastroparesis), kidney injury from dehydration, gallbladder disease, pancreatitis, serious allergic reactions, low blood sugar when combined with insulin or sulfonylureas, and worsening diabetic retinopathy. [2]
- Anesthesia. Rare reports of aspiration into the lungs during general anesthesia or deep sedation have occurred with GLP-1 receptor agonists. [1]
- Birth control pills. The label tells prescribers that oral hormonal contraceptives may be affected after starting and after each increase, and describes backup methods. [1]
- Pregnancy. Weight loss offers no benefit in pregnancy and may cause fetal harm; the label says to stop when pregnancy is recognized. [2] In a lactation study of 11 women, tirzepatide was undetectable in most milk samples. [2] See pregnancy and breastfeeding.
References
- Mounjaro (tirzepatide) prescribing information, Eli Lilly, DailyMed listing dated 2026-09-02. Source. Read 2026-10-22.
- Zepbound (tirzepatide) prescribing information, Eli Lilly, DailyMed listing dated 2026-09-02. Source. Read 2026-10-22.
- Mounjaro EPAR product page, European Medicines Agency. Source. Read 2026-10-22.
- FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss, U.S. Food and Drug Administration. Source. Read 2026-10-22.
- Understanding Unapproved Use of Approved Drugs "Off Label", U.S. Food and Drug Administration. Source. Read 2026-10-22.