Tirzepatide vs Semaglutide: Head-to-Head
Tirzepatide and semaglutide compared on mechanism, weight loss, A1c, side effects, and cost — including the SURMOUNT-5 head-to-head trial data.
Updated May 6, 2026 · 5 min read
The single most-asked GLP-1 question. The short version: in a direct head-to-head trial, tirzepatide produced more weight loss than semaglutide, with comparable side-effect rates. The longer version has a lot of nuance — about who, at what dose, for what goal, and at what cost.
They are not the same molecule
Tirzepatide and semaglutide both act on the GLP-1 pathway, but only tirzepatide is a dual agonist.
| Semaglutide | Tirzepatide | |
|---|---|---|
| Receptors activated | GLP-1 only | GLP-1 + GIP |
| Brand names | Ozempic, Wegovy, Rybelsus | Mounjaro, Zepbound |
| Top approved dose | 2.4 mg (Wegovy) / 2.0 mg (Ozempic) | 15 mg |
| Cadence | Once weekly | Once weekly |
| Half-life | ~7 days | ~5 days |
Why the dose numbers look so different: these are two different molecules with different receptor potencies. You can't compare 2.4 mg of one to 15 mg of the other directly — what matters is the clinical effect at the approved doses, not the milligram count. For a deeper mechanism breakdown, see how tirzepatide works.
Weight loss: tirzepatide has the edge
The SURMOUNT-5 head-to-head trial (published 2025) compared maximum-tolerated-dose tirzepatide against maximum-tolerated-dose semaglutide in adults with obesity but without diabetes:
| Drug | Mean weight loss at 72 weeks |
|---|---|
| Tirzepatide (max tolerated) | ~20% |
| Semaglutide (max tolerated) | ~14% |
That gap — roughly 6 percentage points of body weight — is consistent with the indirect comparison from earlier individual trials (SURMOUNT-1 vs STEP-1). Tirzepatide is the more powerful weight-loss drug in current use.
A few caveats worth holding:
- The placebo arms in obesity trials lose 2–3% of body weight, so both drugs are doing real work. This isn't a small effect getting padded by placebo.
- Individual response varies enormously. Plenty of people lose 20%+ on semaglutide; plenty stall under 10% on tirzepatide. The trial averages tell you about populations, not about you.
- Trial conditions include lifestyle counseling. Real-world results, especially at lower-than-max doses, run a few percentage points lower across the board.
Type 2 diabetes: also tirzepatide, but the gap is smaller
The SURPASS-2 trial put tirzepatide against semaglutide 1 mg head-to-head in T2D:
| Dose | A1c reduction at 40 weeks |
|---|---|
| Tirzepatide 5 mg | -2.0 percentage points |
| Tirzepatide 10 mg | -2.2 |
| Tirzepatide 15 mg | -2.3 |
| Semaglutide 1 mg | -1.9 |
A meaningful but smaller advantage. For most people with T2D, either drug will get them to glycemic targets. Tirzepatide tends to produce slightly better A1c reductions and notably better weight loss as a bonus. See our T2D vs weight loss cluster for how clinicians pick.
Side effects: similar overall, with one swap
The total rate of GI side effects is comparable between the two drugs, but the distribution within "GI side effects" differs:
| Symptom | Semaglutide | Tirzepatide |
|---|---|---|
| Nausea | More common | Slightly less common |
| Constipation | Common | More common |
| Diarrhea | Common | Common |
| Vomiting | Common in early titration | Common in early titration |
| Reflux/heartburn | Common | Common |
The clinical takeaway: if you've struggled with nausea on semaglutide, tirzepatide may be easier — but expect to manage constipation more aggressively. Our side effects vs semaglutide and constipation playbook clusters get into specifics. For coping strategies in general, see the side effects pillar.
Cost: roughly the same on label, different in compounded form
| Semaglutide brand | Tirzepatide brand | |
|---|---|---|
| US list price (commercial) | $1,000–1,400/mo | $1,000–1,400/mo |
| Insurance coverage (T2D) | Common | Common |
| Insurance coverage (obesity) | Patchy | Patchy |
| Compounded availability | Common (still in shortage in some niches) | Limited (FDA shortage resolved late 2024) |
| LillyDirect / Novo direct vials | Available | Available |
Compounded tirzepatide became much harder to access legitimately after the FDA declared the shortage resolved. Compounded semaglutide is in a more ambiguous middle state. If cost is the primary driver, semaglutide tends to be the more accessible option in 2025–2026 for cash-pay patients — see our compounded safety coverage on the semaglutide side.
Switching from one to the other
Switching is uncomplicated. There's no washout. A typical approach:
- Sema → Tirz: start at tirzepatide 2.5 mg the week after your last semaglutide dose, then follow the standard tirzepatide dosing schedule. Some clinicians skip 2.5 and start at 5 mg if you were stable on semaglutide ≥ 1 mg.
- Tirz → Sema: start at semaglutide 0.25 mg the week after your last tirzepatide dose, then follow the standard semaglutide dosing schedule. Same logic — your prescriber may start higher if you were on a stable tirzepatide dose.
Side effects often re-appear briefly during a switch even if you were tolerating the previous drug well. Don't read it as the new drug being worse — it's usually a re-titration effect that fades within 2–3 weeks.
So which should you pick?
- Free choice, weight-loss goal → tirzepatide tends to produce more weight loss with similar tolerability.
- History of bad nausea → tirzepatide may be more tolerable.
- History of stubborn constipation → semaglutide may be easier.
- Insurance covers one but not the other → take the covered one.
- Cash-pay with cost as the limiting factor → compounded semaglutide is currently easier to source legitimately than compounded tirzepatide.
- Already on one and doing well → don't switch on theory. Real tolerance and adherence beat marginal trial differences.