Semaglutide vs tirzepatide: the head-to-head trial
Semaglutide and tirzepatide are the two incretin peptides most people in the Philippines are choosing between. Only one published trial has put them head to head. Here is what it found, how the two differ, and what each costs per milligram as a research vial.
In the only head-to-head trial, SURMOUNT-5, adults with obesity lost 20.2% of body weight on average with tirzepatide against 13.7% with semaglutide over 72 weeks, and slightly fewer stopped tirzepatide because of side effects. Tirzepatide acts on two receptors; semaglutide on one.
Semaglutide vs tirzepatide, side by side
| Semaglutide | Tirzepatide | |
|---|---|---|
| Receptors | GLP-1 | GIP and GLP-1 |
| Head-to-head weight change (SURMOUNT-5, 72 weeks) | -13.7% | -20.2% |
| Stopped because of side effects (SURMOUNT-5) | 8.0% | 6.1% |
| Stopped because of stomach and gut side effects | 5.6% | 2.7% |
| Own placebo-controlled trial | STEP 1: -14.9% vs -2.4% at 68 weeks | SURMOUNT-1: up to -20.9% at 72 weeks |
| Registered in the Philippines | Yes, as prescription medicines | See FDA Philippines verification portal |
The SURMOUNT-5 trial
SURMOUNT-5 was a 72-week, open-label phase 3b trial in 751 adults with obesity and without type 2 diabetes. Each person took the highest dose of their assigned medicine they could tolerate. Tirzepatide produced an average weight change of -20.2% against -13.7% for semaglutide, a difference that was statistically significant.
Side effects in both groups were mainly stomach and gut related and mostly mild to moderate. The developer notes the trial was not designed to compare safety and tolerability.
Aronne et al., NEJM 2025 (SURMOUNT-5). Separate trials: STEP 1 and SURMOUNT-1.
How they work
Both are synthetic versions of gut hormones called incretins. Semaglutide mimics GLP-1. Tirzepatide is a single molecule that acts on both the GLP-1 and GIP receptors. Retatrutide, the newer compound, adds the glucagon receptor as well. More in GLP-1 peptides in the Philippines.
Side effects of tirzepatide in detail: tirzepatide side effects.
Price per milligram in the Philippines
| Research vial | Vial | Price | Per mg |
|---|---|---|---|
| Semaglutide | 15mg | ₱1,990 ($33) | ₱133 |
| Tirzepatide | 15mg | ₱1,890 ($32) | ₱126 |
| Retatrutide | 15mg | ₱2,990 ($50) | ₱199 |
Primara Labs' listed prices, read 28 September 2026. Research vials are not the registered medicines and are not approved for use in people.
Semaglutide
A GLP-1 receptor agonist.
Tirzepatide
A dual agonist of the GIP and GLP-1 receptors.
Retatrutide
A triple agonist of the GIP, GLP-1 and glucagon receptors.
And retatrutide?
Retatrutide is the compound many Philippine buyers ask about next. Its phase 2 trial reported up to 24.2% average weight loss at 48 weeks, but it has not been tested head to head against either compound in a published trial and it is not approved anywhere. See the retatrutide page.
If you are choosing between these for your own health, that is a decision for a licensed physician, who can prescribe the registered medicines.
Questions
Is tirzepatide better than semaglutide?
In the SURMOUNT-5 head-to-head trial, adults with obesity lost an average of 20.2% of body weight on tirzepatide against 13.7% on semaglutide over 72 weeks. Better for weight loss on average in that trial; whether it is better for a specific person is a question for a physician.
What is the difference between semaglutide and tirzepatide?
Semaglutide acts on one receptor, GLP-1. Tirzepatide acts on two, GIP and GLP-1. Both are weekly injectable peptides.
Which has fewer side effects, semaglutide or tirzepatide?
In SURMOUNT-5, 8.0% stopped semaglutide and 6.1% stopped tirzepatide because of side effects, mostly stomach and gut related. The trial was not designed to compare safety.
How much do semaglutide and tirzepatide cost in the Philippines?
As research vials at Primara Labs, semaglutide 15mg is ₱133 per mg and tirzepatide 15mg is ₱126 per mg, checked 28 September 2026. Prescription medicines are priced separately by pharmacies.
Where does retatrutide fit?
Retatrutide adds a third receptor, glucagon. It has not been compared head to head with either in a published trial and is not approved anywhere.
Not medical or legal advice. Peptides sold as research compounds are not registered medicines with FDA Philippines and are not approved for use in people. If you are thinking about any compound for your own health, speak to a licensed physician first.
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Keep reading
Tirzepatide side effects: what the trials reported
Side effect rates from the published trial, the official warnings, and the comparison with semaglutide.
Read the guide →BuyingGLP-1 peptides in the Philippines: retatrutide vs tirzepatide vs semaglutide
The three incretin compounds side by side: receptors, trials, approval and price per mg.
Read the guide →BuyingPeptide prices in the Philippines
Every product priced in pesos and dollars, per vial and per milligram, with a comparison calculator.
Read the guide →