Tirzepatide, Explained
What tirzepatide is, how its dual mechanism differs from semaglutide, and how to vet the clinic prescribing it.
What is tirzepatide?
How does tirzepatide's dual mechanism work?
Semaglutide activates one receptor: GLP-1. Tirzepatide activates two: GIP and GLP-1. Both are gut hormones involved in appetite and blood sugar. Tirzepatide was engineered from the native GIP peptide with GLP-1 activity built in, and that dual action is the main thing that sets it apart. It is a once-weekly subcutaneous injection, approved for adults with a BMI of 30 or higher, or 27 or higher with at least one weight-related condition. There is no oral form.
What are the FDA-approved forms?
As with semaglutide, the molecule is one thing and the brands are different approvals of it. Compounded tirzepatide is a separate, non-FDA-approved category covered in our compounded vs brand guide.
| Brand | Approved for | Form | Max dose |
|---|---|---|---|
| Zepbound | Weight loss; moderate-to-severe OSA in adults with obesity | Weekly injection | 15 mg |
| Mounjaro | Type 2 diabetes | Weekly injection | 15 mg |
Zepbound also carries an FDA indication for moderate-to-severe obstructive sleep apnea (OSA) in adults with obesity, used alongside a reduced-calorie diet and increased physical activity. Mounjaro is frequently prescribed off-label for weight loss, similar to how Ozempic is used for the same purpose. Both brands are made by Eli Lilly and are identical in dosing and delivery.
How is tirzepatide dosed?
Tirzepatide starts at 2.5 mg weekly and increases gradually to limit side effects. There are three official maintenance doses: 5 mg, 10 mg, and 15 mg. Unlike semaglutide, which has a single target dose, tirzepatide gives the prescriber room to stop at whichever dose balances results and tolerability for a given patient. A responsible clinic follows a documented titration schedule.
Is tirzepatide better than semaglutide? What the trials show.
The SURMOUNT program is the largest trial series for tirzepatide in weight management. Three results matter most:
- SURMOUNT-1 (2022, NEJM): 2,539 adults without diabetes over 72 weeks. Mean weight loss was 15.0% at 5 mg, 19.5% at 10 mg, and 22.5% at 15 mg, versus 3.1% on placebo. At 15 mg, 91% lost at least 5% of body weight and 57% lost 20% or more.
- SURMOUNT-2 (2023): In adults with type 2 diabetes and obesity, the 15 mg dose produced 14.7% weight loss. Diabetes tends to blunt the weight-loss response, which is consistent across GLP-1 medications.
- SURMOUNT-5 (2025, NEJM): The first head-to-head comparison against semaglutide. Over 72 weeks, the tirzepatide arm averaged 20.2% weight loss versus 13.7% for the semaglutide arm, both trial-arm averages after each was titrated to its maximum tolerated dose, a statistically superior result.
These are averages. Individual response varies by 10 percentage points or more in either direction, and some people respond better to semaglutide for reasons not fully understood. As with semaglutide, weight regain after stopping is documented: SURMOUNT-4 showed that patients switched from tirzepatide to placebo regained roughly half of their lost weight over about a year. A maintenance plan is something to discuss with your provider before starting.
| Trial arm | Mean weight loss |
|---|---|
| Tirzepatide | 20.2% |
| Semaglutide | 13.7% |
What are the side effects and contraindications?
Side effects are primarily gastrointestinal and broadly comparable to semaglutide: nausea, diarrhea, vomiting, constipation, and injection-site reactions, mostly clustered around dose increases. The dual mechanism does not appear to meaningfully increase GI side-effect rates.
Tirzepatide carries a boxed warning for thyroid C-cell tumors observed in rodent studies, the same as semaglutide. It is contraindicated in people with a personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia type 2 (MEN 2). Other risks include pancreatitis, gallbladder disease, and hypoglycemia when combined with insulin or sulfonylureas. Note that, unlike Wegovy, tirzepatide is not currently FDA-approved for cardiovascular risk reduction. A legitimate clinic screens for these before prescribing. This is not medical advice.
What does tirzepatide cost, brand versus compounded?
| Option | Typical monthly cost | FDA-approved? |
|---|---|---|
| Brand-name Zepbound (no insurance) | $1,200–$1,600 | Yes |
| Compounded tirzepatide (503A/503B) | $250–$500 | No |
Compounded tirzepatide typically runs $50 to $100 more per month than compounded semaglutide. Insurance coverage varies, and Mounjaro is often more widely covered than Zepbound, which is why some providers prescribe Mounjaro off-label to reach better coverage. As with semaglutide, the lower compounded price reflects the absence of FDA oversight, not a discount on the same product. For a fuller breakdown, see our GLP-1 cost guide.
How should you choose a tirzepatide clinic?
Tirzepatide is newer than semaglutide, so fewer providers carry it, and telehealth is common. The vetting questions are the same regardless of which drug: a named licensed prescriber, a real evaluation before prescribing, screening for contraindications, disclosed medication sourcing with a named pharmacy, required baseline labs, and published pricing.
Those are the dimensions GLP-1 Grades scores. See our grading methodology for the weighting, compare graded clinics side by side, and check our semaglutide guide if you are weighing the two.
This guide is informational and is not medical advice. It does not recommend taking any medication. Decisions about tirzepatide should be made with a licensed healthcare provider who knows your history.