GLP-1 Comparison
Ozempic vs Mounjaro
Semaglutide (Ozempic, Wegovy) vs tirzepatide (Mounjaro, Zepbound) — weight loss outcomes, pharmacokinetics, side effects, and who each medication tends to suit best.
Based on STEP 1 (semaglutide, NEJM 2021) and SURMOUNT-1 (tirzepatide, NEJM 2022) clinical trial data.
Semaglutide
Ozempic · Wegovy
Tirzepatide
Mounjaro · Zepbound
At a glance
The key mechanism difference
Semaglutide activates only the GLP-1 receptor — which slows gastric emptying, reduces appetite, and improves blood sugar. Tirzepatide activates both the GIP and GLP-1 receptors.
GIP activation adds an additional appetite and fat-storage pathway, which is why tirzepatide consistently produces greater weight loss in head-to-head data — not because it's a "stronger" GLP-1, but because it's working through an additional receptor.
Weight loss outcomes
Important context: These are trial averages on the maximum-dose escalation schedule. Real-world results are lower and vary widely by dose, diet, genetics, and time at dose. Most people don't reach maximum dose.
Pharmacokinetics — what the half-life means for you
Semaglutide — 7-day half-life
- • Drug levels stay relatively stable week to week
- • Side effects (especially nausea) can persist throughout the week
- • Levels decline slowly if you stop — ~5–7 weeks to clear
- • If you miss a dose, levels drop more gradually
Tirzepatide — 5-day half-life
- • Slightly more variability in weekly levels
- • GI side effects may ease faster mid-week for some
- • Clears system in ~4–5 weeks
- • A missed dose has a sharper impact on drug levels
Both peak around Day 1–2 after injection (Tmax ~1–1.5 days), which is why side effects typically hit hardest in the first couple of days after your shot.
Side effects compared
Tirzepatide generally shows lower rates of nausea and vomiting in trials, possibly due to the GIP component tempering GI effects. That said, individual responses vary significantly — some people do better on semaglutide.
Which is right for you?
This is entirely your provider's call based on your health history, insurance coverage, and individual response. But here's what the data suggests:
Consider semaglutide if:
- • You have better insurance coverage for Ozempic/Wegovy
- • Your primary goal is modest weight loss (10–15%)
- • You want a well-established, longer-tracked safety record
- • You've had good early results on semaglutide already
Consider tirzepatide if:
- • You're targeting maximum weight loss outcome
- • You've plateaued or had limited response on semaglutide
- • You have type 2 diabetes (additional glycemic benefit)
- • GI side effects on semaglutide have been significant
Cost and insurance coverage are the most common practical deciding factor — both medications can be $1,000+/month without coverage.
Switching between them
Switching from semaglutide to tirzepatide (or vice versa) is common and generally safe, but the timing and starting dose matters. Semaglutide's 7-day half-life means it stays in your system for weeks — starting tirzepatide too soon means both drugs are active simultaneously.
Most providers wait 1–2 weeks after the last semaglutide dose before starting tirzepatide, and typically start at the lowest tirzepatide dose regardless of where you were on semaglutide. Always follow your provider's guidance — don't switch without a plan.
See your drug level right now
Both drugs follow the Bateman equation — see exactly where you are in your weekly cycle.
Check drug level →What to expect at your dose
Clinical trial benchmarks for every dose level on both medications.
Your journey guide →Data from STEP 1 (Wilding et al., NEJM 2021) and SURMOUNT-1 (Jastreboff et al., NEJM 2022). Individual results vary. Not medical advice — always discuss treatment decisions with your provider.