Tirzepatide vs Semaglutide: Weight Loss, Cost & Switching
The most-asked GLP-1 question on the internet: tirzepatide vs semaglutide. Real trial data, side-effect comparison, switching protocol, and a dose conversion calculator.
01 At a glance
| Feature | Tirzepatide | Semaglutide |
|---|---|---|
| Mechanism | GLP-1 + GIP dual agonist | GLP-1 only |
| Brand names | Mounjaro, Zepbound | Ozempic, Wegovy, Rybelsus |
| Manufacturer | Eli Lilly | Novo Nordisk |
| FDA approval (weight) | 2023 (Zepbound) | 2021 (Wegovy) |
| Avg. weight loss | 20.9% @ 15 mg (72 wks) | 14.9% @ 2.4 mg (68 wks) |
| Doses available | 2.5–15 mg | 0.25–2.4 mg |
| Frequency | Weekly subcutaneous | Weekly subcutaneous |
| Brand monthly retail | $1,086 (Zepbound) | $1,349 (Wegovy) |
| Compounded monthly | $199–$329 | $179–$299 |
| Sleep apnea approval | Yes (Zepbound, 2024) | No |
| Cardiovascular approval | Yes (Zepbound, 2024) | Yes (Wegovy, 2024) |
02 The mechanism difference: GLP-1 vs GLP-1 + GIP
Both drugs mimic gut hormones that regulate appetite, gastric emptying, and insulin response. The structural difference: tirzepatide is a dual agonist that activates two incretin receptors at once.
Semaglutide
Activates only the GLP-1 receptor. GLP-1 (glucagon-like peptide-1) is one of two main incretin hormones. When activated, it slows stomach emptying, dampens hunger signals in the brain, and stimulates insulin release in a glucose-dependent way.
Tirzepatide
Activates both the GLP-1 receptor and the GIP receptor. GIP (glucose-dependent insulinotropic polypeptide) is the other major incretin. The combination produces stronger appetite suppression and additional metabolic effects on fat tissue and energy expenditure that GLP-1 alone doesn't achieve.
Whether the GIP arm matters because of GIP agonism or partial agonism remains debated in the literature, but the clinical effect is clear: tirzepatide produces meaningfully more weight loss than semaglutide at maximum doses.
03 Weight loss head-to-head
SURPASS-2: the only direct comparison
SURPASS-2 (Frias et al., NEJM 2021) randomized 1,879 adults with type 2 diabetes to either tirzepatide (5/10/15 mg) or semaglutide 1.0 mg weekly for 40 weeks. Primary endpoint was HbA1c change; weight change was a key secondary endpoint.
| Treatment | Mean weight change @ 40 wks | HbA1c change |
|---|---|---|
| Tirzepatide 5 mg | −7.6 kg | −2.01% |
| Tirzepatide 10 mg | −9.3 kg | −2.24% |
| Tirzepatide 15 mg | −11.2 kg | −2.30% |
| Semaglutide 1.0 mg | −5.7 kg | −1.86% |
Source: SURPASS-2, n=1,879 adults with type 2 diabetes, 40 weeks. Note semaglutide arm used 1.0 mg (the diabetes maximum at the time), not the 2.4 mg weight-loss dose.
SURMOUNT-1 vs STEP-1 (cross-trial comparison)
These were the pivotal trials for weight-loss approval — different populations, different durations, but the most-cited numbers in the public conversation:
| Trial | Drug | Dose | Avg. weight loss | Duration |
|---|---|---|---|---|
| SURMOUNT-1 | Tirzepatide | 15 mg | −20.9% | 72 weeks |
| SURMOUNT-1 | Tirzepatide | 10 mg | −19.5% | 72 weeks |
| SURMOUNT-1 | Tirzepatide | 5 mg | −15.0% | 72 weeks |
| STEP-1 | Semaglutide | 2.4 mg | −14.9% | 68 weeks |
The headline: at maximum approved doses for weight loss, tirzepatide produces about 40% more weight loss than semaglutide. Cross-trial comparisons aren't perfect, but the magnitude is consistent across multiple analyses.
04 Side effects: roughly equivalent
Both drugs have GI-dominated side effect profiles. Common rates from each trial:
| Side effect | Tirzepatide 15 mg | Semaglutide 2.4 mg |
|---|---|---|
| Nausea | 31% | 44% |
| Diarrhea | 23% | 30% |
| Constipation | 12% | 24% |
| Vomiting | 13% | 24% |
| Dyspepsia | 8% | 11% |
Side-effect rates trend slightly lower for tirzepatide at max dose vs semaglutide at max weight-loss dose — though direct head-to-head data on this exact comparison is limited. Practical takeaway: both drugs are well tolerated for the majority, both produce GI symptoms during titration, and the experience is more similar than different.
05 Cost comparison
| Tier | Tirzepatide (Zepbound) | Semaglutide (Wegovy) |
|---|---|---|
| Brand retail | $1,086/mo | $1,349/mo |
| Manufacturer direct | $349–$599/mo | $499/mo (NovoCare) |
| Compounded telehealth | $199–$329/mo | $179–$299/mo |
| With insurance + savings card | $25/mo | $0–$25/mo |
Brand-name tirzepatide is cheaper than brand-name semaglutide at retail. Compounded prices are similar across both molecules. With insurance and copay assistance, both can hit $0–$25/month. The cost-driven case for either drug is mostly a wash; the effectiveness-driven case favors tirzepatide for weight loss.
06 Switching from semaglutide to tirzepatide
Switching is common in 2026 — most often because patients on semaglutide have plateaued, want more weight loss, or have heard about the SURPASS-2 data. The standard protocol:
- Stop semaglutide for at least 1 week. Some prescribers do 1–2 weeks; few wait longer because semaglutide has a long half-life (1 week).
- Start tirzepatide at the low equivalent dose. Use the converter below or err on the lower side.
- Re-titrate weekly for the first 2–3 weeks if tolerating well, then switch to the standard 4-week titration interval.
- Watch for GI symptoms. Initial nausea is common because you're effectively re-starting a GLP-1.
- Don't combine the two drugs. They are not synergistic, just additive on side effects. Choose one.
07 Semaglutide ↔ tirzepatide dose converter
Use the converter to estimate a starting dose when switching between molecules. Always discuss the actual switch with your prescriber.
Semaglutide ↔ Tirzepatide Dose Converter
ConverterA clinically reasonable dose-equivalence guide for patients switching between semaglutide (Ozempic/Wegovy) and tirzepatide (Mounjaro/Zepbound). Always confirm switches with your prescriber.
- From
- 1.0 mg semaglutide
- To (start at)
- 5 mg tirzepatide
*Conversion guide only. Real-world switches require titration, medical evaluation, and may vary based on tolerance, insurance, and clinical goals.
08 Which should you choose?
Choose tirzepatide if…
- Your primary goal is maximum weight loss
- You've plateaued on semaglutide
- You need cardiovascular benefit AND want the largest weight effect
- You also have or want OSA treatment (Zepbound is approved for moderate-severe OSA)
- You want the cheapest brand-name option (Zepbound < Wegovy)
Stick with semaglutide if…
- You're tolerating it well and meeting your goals
- You have it covered by insurance and tirzepatide isn't
- You want an oral option (only Rybelsus / oral semaglutide exists)
- You're a low-side-effect responder
- Your prescriber recommends it for cardiovascular reasons
Switch to tirzepatide online.
Most telehealth providers can prescribe tirzepatide whether you're new to GLP-1s or switching from semaglutide. They'll handle the transition protocol.
Get Tirzepatide Online→09 Tirzepatide vs semaglutide FAQ
For weight loss, yes — by a meaningful margin. The pivotal head-to-head trial (SURPASS-2) showed tirzepatide produced about 1.5–2× more weight loss at comparable doses in patients with type 2 diabetes. SURMOUNT-1 showed 20.9% loss at 15 mg tirzepatide vs STEP-1's 14.9% loss at 2.4 mg semaglutide. Tirzepatide's GLP-1 + GIP dual mechanism is more potent for weight management. Side-effect profiles are roughly similar.
Both are weekly injectable peptide medications. The key difference is mechanism: semaglutide is a single GLP-1 receptor agonist; tirzepatide is a dual GLP-1 + GIP agonist. The added GIP arm is responsible for tirzepatide's greater weight-loss effect. Brand names also differ: semaglutide is Ozempic/Wegovy/Rybelsus (Novo Nordisk); tirzepatide is Mounjaro/Zepbound (Eli Lilly).
No. They are different molecules made by different companies. Tirzepatide and semaglutide are both peptide medications and both target GLP-1, but tirzepatide additionally targets GIP, while semaglutide does not. They are not interchangeable, not generic versions of each other, and pharmacies cannot substitute one for the other.
Yes, this is a common transition. The standard approach is to stop semaglutide for one full week, then start tirzepatide at a low equivalent dose (usually 2.5–5 mg) and re-titrate weekly to assess tolerance. Going one-for-one (e.g., from 1 mg semaglutide directly to 5 mg tirzepatide) is generally not recommended. Use the converter above for typical equivalences.
There's no FDA-published equivalence. Clinically reasonable rough conversions: 0.25–0.5 mg semaglutide ≈ 2.5 mg tirzepatide; 1.0 mg semaglutide ≈ 5 mg tirzepatide; 1.7 mg semaglutide ≈ 5–7.5 mg tirzepatide; 2.0 mg semaglutide ≈ 7.5 mg tirzepatide; 2.4 mg semaglutide ≈ 7.5 mg tirzepatide. Always start at the low end and re-titrate.
Brand-name Zepbound (tirzepatide) is cheaper than brand-name Wegovy (semaglutide) by about $260/month — $1,086 vs $1,349 retail. Compounded versions are similar: tirzepatide compounded runs $199–$329/month, semaglutide compounded runs $179–$299/month. So semaglutide compounded is marginally cheaper, but tirzepatide brand is meaningfully cheaper than semaglutide brand.
Tirzepatide. SURPASS-2 (head-to-head in T2D) showed tirzepatide caused 11.2 kg loss vs 5.7 kg for semaglutide at the highest doses. SURMOUNT-1 (tirzepatide weight-loss trial) reported 20.9% mean loss at 15 mg over 72 weeks. STEP-1 (semaglutide weight-loss trial) reported 14.9% mean loss at 2.4 mg over 68 weeks. The difference is real and clinically significant.
They're very similar — both are dominated by GI symptoms (nausea, diarrhea, constipation, vomiting) that peak with dose escalation and improve with stability. Tirzepatide may have slightly higher peak nausea rates at the maximum dose (15 mg) vs semaglutide at 2.4 mg, but the trial populations and dose-equivalences are not directly comparable. In real-world telehealth practice, the side effect experience is largely similar.
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