Semaglutide vs Tirzepatide
A plain-English comparison of the two most-researched GLP-1 based protocols: how they work, how they're dosed, what the trial data shows, and how side effects differ.
Semaglutide
Single GLP-1 receptor agonist. Slows gastric emptying, boosts glucose-dependent insulin release and reduces appetite via CNS GLP-1 signaling.
Tirzepatide
Dual GIP + GLP-1 receptor agonist. Adds GIP activity, which in clinical data amplifies weight loss and glycemic control beyond GLP-1 alone.
Typical research dosing
Both are subcutaneous weekly injections, titrated slowly to minimize GI side effects. Never self-adjust without a prescriber.
| Week | Semaglutide | Tirzepatide |
|---|---|---|
| 1–4 | 0.25 mg | 2.5 mg |
| 5–8 | 0.5 mg | 5 mg |
| 9–12 | 1.0 mg | 7.5 mg |
| 13–16 | 1.7 mg | 10 mg |
| 17–20 | 2.4 mg | 12.5 mg |
| 21+ | 2.4 mg (maintenance) | 15 mg (max) |
Weight loss data
- Semaglutide 2.4 mg (STEP 1): ~14.9% mean body weight loss at 68 weeks.
- Tirzepatide 15 mg (SURMOUNT-1): ~20.9% mean body weight loss at 72 weeks.
- Head-to-head SURPASS-2 (T2D): tirzepatide 15 mg beat semaglutide 1 mg on A1C and weight.
- Boxed warning: thyroid C-cell tumors in rodents — avoid with personal or family history of medullary thyroid carcinoma or MEN 2.
- Most common side effects: nausea, diarrhea, constipation, reduced appetite (usually worst during titration).
- Rare but serious: pancreatitis, gallbladder disease, kidney injury from dehydration.
- Not for use in pregnancy. Discuss any GLP-1 protocol with your prescriber.
FAQ
What is the main difference between semaglutide and tirzepatide?
Semaglutide is a single GLP-1 receptor agonist. Tirzepatide is a dual agonist that activates both GIP and GLP-1 receptors, which appears to produce greater average weight loss in clinical trials.
Which produces more weight loss, semaglutide or tirzepatide?
In head-to-head data (SURMOUNT and STEP program comparisons), tirzepatide showed higher average weight reduction — roughly 20–22% at the top dose versus about 15% for semaglutide 2.4 mg over 68–72 weeks. Individual response varies.
How are they dosed?
Both are weekly subcutaneous injections. Semaglutide titrates 0.25 → 0.5 → 1.0 → 1.7 → 2.4 mg weekly. Tirzepatide titrates 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg weekly, moving up every 4 weeks as tolerated.
Do they share the same side effects?
Yes — the most common are nausea, diarrhea, constipation and reduced appetite, mostly during titration. Both carry a boxed warning for thyroid C-cell tumors in rodents and are contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2.
Can you switch from semaglutide to tirzepatide?
Switching is common but should be done under a prescriber's guidance. A typical approach is to restart at the lowest tirzepatide dose (2.5 mg) after the last semaglutide dose has cleared, then titrate up.
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Educational content, not medical advice. Semaglutide and tirzepatide are prescription medications; discuss any protocol with a licensed clinician.