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The dad-test answer
Tirzepatide loses more weight and drops A1C harder in head-to-head trials, but it costs more, hits the gut harder for some people, and has a shorter track record. Semaglutide is the easier on-ramp; tirzepatide is the heavier hitter.
Who wins for what
| Use case | Who wins, and why |
|---|---|
| weight loss |
tirzepatide SURMOUNT-5 head-to-head: 20.2% loss on tirzepatide vs 13.7% on semaglutide at 72 weeks. |
| type 2 diabetes (A1C) |
tirzepatide SURPASS-2: A1C drop 2.30% on tirzepatide vs 1.86% on semaglutide at 40 weeks. |
| cost / access |
semaglutide Wegovy/Ozempic launched in 2017 - more insurance coverage and a deeper compounding pharmacy market. |
| tolerability for first-timers |
semaglutide GI side effects roughly 5-10% higher on tirzepatide in head-to-head trials; longer track record at the standard doses. |
What the head-to-head data shows
We have an actual head-to-head trial here, which is rare. SURMOUNT-5 (Aronne et al., NEJM 2025) randomized 751 adults with obesity and no diabetes to maximum-tolerated tirzepatide vs maximum-tolerated semaglutide for 72 weeks: tirzepatide produced 20.2% body-weight loss vs 13.7% on semaglutide. SURPASS-2 (Frias et al., NEJM 2021) compared the two in Type 2 diabetes patients - tirzepatide dropped A1C 2.30% at 15mg vs 1.86% on semaglutide 1mg over 40 weeks. The original FDA approval of Zepbound (tirzepatide for obesity, 2023) drew on the SURMOUNT-1 trial showing 22.5% peak weight loss. Semaglutide's STEP-1 trial (Wilding et al., NEJM 2021) showed 14.9% loss at 68 weeks. Both molecules carry a black-box warning for thyroid C-cell tumors based on rodent data.
Our honest call
If you can get tirzepatide and tolerate the GI ramp, it is the heavier hitter. Roughly 6-7 percentage points more weight loss in head-to-head data is not a rounding error. But semaglutide has the longer real-world track record, deeper insurance coverage in 2026, and broader compounding pharmacy availability for the people who go that route. Our default suggestion: if a normal reader is starting fresh and has access to either, start with tirzepatide. If a reader is already on semaglutide and tolerating it, the switch is only worth it if weight loss has stalled below the goal - read the switcher protocol before pulling the trigger.
Sources and citations
- Aronne et al., SURMOUNT-5 head-to-head trial, NEJM 2025 (PMID 40374016)
- Frias et al., SURPASS-2 trial, NEJM 2021 (PMID 34170647)
- Wilding et al., STEP-1 trial, NEJM 2021 (PMID 33567185)
- FDA Zepbound prescribing label (approved Nov 2023)
- FDA Wegovy prescribing label (approved Jun 2021)
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Last reviewed · 2026-05-07 · Page generated by Protocol One matrix engine. None of this replaces a doctor. Peptides are gray-market in the US for most uses. Talk to a real prescriber before you change anything.