Tirzepatide
A once-weekly injection that acts on two gut-hormone receptors. Its obesity trial is among the largest on this site, and a withdrawal trial measured what happens when it stops.
- U.S. status
- FDA-approved
- Zepbound (tirzepatide) injection, NDA 217806, approved for chronic weight management.
- FDA source, read September 2026.
- Evidence cited here
- Weight: Large trials1 randomized trial of 1,000 or more people cited here for weight.
- Forms sold
- Injection · Oral · Sublingual · Topical
1. What Tirzepatide is
Tirzepatide acts on two receptors, GIP and GLP-1, which respond to hormones released after eating. It is approved for chronic weight management as Zepbound, a once-weekly injection.
Most telehealth sellers dispense compounded tirzepatide rather than Zepbound. A compounded preparation is not FDA-approved, and the FDA does not review it for safety, effectiveness or quality before it is dispensed.
2. How it works
Tirzepatide is a single molecule built to activate both the GIP receptor and the GLP-1 receptor. Through the GLP-1 receptor it slows stomach emptying and reduces appetite, as semaglutide does; what the GIP activity adds in people is still being worked out.
It is injected once a week. The dose rises in steps over the first months; in SURMOUNT-1, stomach side effects occurred mainly during that escalation.
3. What the studies measured
SURMOUNT-1 randomized 2,539 adults with obesity or overweight, without diabetes, to 5, 10 or 15 mg weekly or placebo for 72 weeks. Weight fell 15.0%, 19.5% and 20.9% on the three doses, against 3.1% on placebo. Adverse events led 4.3% to 7.1% of the tirzepatide groups to stop, against 2.6% on placebo.
SURMOUNT-4 gave everyone tirzepatide for 36 weeks, with a mean loss of 20.9%, then randomized 670 people to continue or switch to placebo. Over the next 52 weeks the continuing group lost a further 5.5%, and the placebo group regained 14.0%.
4. What they did not measure
Both trials used the approved product. Neither tested a compounded preparation, so the numbers describe Zepbound, not a pharmacy's version of it.
These trials compared tirzepatide with placebo, not with semaglutide. Neither abstract reports how often nausea occurred, only that stomach side effects were the most common.
The studies behind this page
The evidence label above is computed from these papers: their design and how many people they enrolled.
- Randomized trial
2,539 people
Counts toward: Weight
Mean weight change of −15.0%, −19.5% and −20.9% by dose, against −3.1% on placebo.
Adults with obesity or overweight, without diabetes; 5, 10 or 15 mg weekly or placebo for 72 weeks.
Jastreboff AM, Aronne LJ, Ahmad NN, Wharton S, Connery L, Alves B, et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. PMID 35658024
- Randomized trial
670 people
Counts toward: Weight
Weight change of −5.5% with continued tirzepatide against a 14.0% regain on placebo.
Adults who lost weight over a 36-week open-label lead-in, randomized to continue or switch to placebo for 52 weeks.
Aronne LJ, Sattar N, Horn DB, Bays HE, Wharton S, Lin WY, et al. (2024). Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA. PMID 38078870
Tirzepatide
Frequently asked questions
- Is compounded tirzepatide the same as Zepbound?
- It is meant to contain the same molecule, but only Zepbound is FDA-approved and was tested in SURMOUNT-1. A compounded preparation is made by a pharmacy and is not reviewed by the FDA before it reaches you.
- Does the weight come back after stopping tirzepatide?
- In SURMOUNT-4, people switched to placebo regained 14.0% of their body weight over 52 weeks, while those who continued lost a further 5.5%.