Which causes more weight loss — semaglutide or tirzepatide?

Clinical trials show tirzepatide achieved greater average weight loss: 15–22% of body weight (SURMOUNT trials) compared to 12–15% for semaglutide (STEP trials). However, both are significantly more effective than lifestyle changes alone, and individual results vary substantially.

Are the side effects different?

Both have similar GI side effects: nausea, vomiting, diarrhea, and constipation — especially during dose escalation. These typically improve after the first few weeks. Tirzepatide's side effect profile is broadly similar, though some report GI symptoms are manageable at a comparable rate.

Which is cheaper — semaglutide or tirzepatide?

Semaglutide is generally cheaper. Compounded semaglutide starts around $150–$350/month online; compounded tirzepatide typically starts around $250–$500/month. Brand-name costs are higher for both without insurance.

Can I switch from semaglutide to tirzepatide?

Yes, but it requires a new prescription and a dose reset. You'd start at tirzepatide's starting dose (2.5mg weekly) regardless of what dose you were on with semaglutide. Discuss the transition with your prescribing provider.

Which drug is easier to get through online programs?

Semaglutide is more widely available through online programs — nearly all providers offer it. Tirzepatide availability is more limited and can change as FDA regulations on compounding evolve. Check your preferred provider's current state availability.

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Last updated April 2026 · How we research

Semaglutide vs tirzepatide: which is better for weight loss?

Tirzepatide shows stronger average weight loss in clinical trials. Semaglutide is more widely available and generally cheaper. Both work by reducing appetite. Here's what the data actually says and how to pick between them.

The gist

Tirzepatide led to ~21% average weight loss in SURMOUNT-1; semaglutide ~15% in STEP 1.
Both reduce appetite; tirzepatide adds a second receptor (GIP) on top of GLP-1.
Semaglutide is usually cheaper and more widely available, so the choice often comes down to cost and goals.

Side-by-side comparison

Factor	Semaglutide	Tirzepatide
Mechanism	GLP-1 agonist	GLP-1 + GIP dual agonist
Brand names	Ozempic, Wegovy	Mounjaro, Zepbound
Avg weight loss (trials)	~12–15%	~15–22%
Compounded cost (online)	~$150–$350/mo	~$250–$500/mo
Injection frequency	Once weekly	Once weekly
Online availability	Very widely available	Available, but fewer programs
Common side effects	Nausea, GI upset	Nausea, GI upset (similar)

Trial data from STEP 1 (NEJM, 2021) and SURMOUNT-1 (NEJM, 2022).

2026 update: The FDA approved Wegovy HD (semaglutide 7.2mg) in March 2026. The STEP UP trial showed 20.7% mean weight loss at 72 weeks — nearly matching tirzepatide's numbers in separate trials. The two drugs have not been compared head-to-head.

Which should you start with?

Start with semaglutide if:

• Budget is a concern — semaglutide is meaningfully cheaper per month
• You want maximum availability and provider options
• You're new to GLP-1s and want to start with the more established option

Consider tirzepatide if:

• Maximizing weight loss is the primary goal and cost is less of a factor
• You've tried semaglutide with limited response and want to try the dual-action mechanism
• Your provider recommends it based on your health profile

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Frequently Asked Questions

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Sources

Related: Semaglutide online cost

Related: Tirzepatide online cost

Related: Best GLP-1 programs overall

Medical Disclaimer: This page is for informational purposes only and does not constitute medical advice. Peptides and GLP-1 medications require a prescription and should only be taken under the supervision of a licensed healthcare provider. Individual results vary. Always consult a doctor before starting any new medication or compound.