Retatrutide vs Semaglutide
First generation versus third. How big is the gap, and what do you give up to close it?
Reviewed by the amino101 editorial team. , first published .
Semaglutide is the drug that made GLP-1 a household term and retatrutide is the one that may replace the whole class. Semaglutide activates one receptor and produced about 15 percent weight loss over 68 weeks in STEP 1. Retatrutide activates three, GLP-1, GIP and glucagon, and produced about 24 percent at 48 weeks in phase 2, with Lilly reporting roughly 28 percent at 80 weeks in the 2026 TRIUMPH-1 topline. That is nearly double the semaglutide figure, though from different trials and with the retatrutide number still unpublished in full. Everything else favors semaglutide. It has been approved since 2017, has the SELECT cardiovascular outcomes trial, an oral form, millions of patient years, and the cheapest supply in the class. Retatrutide is not approved anywhere, has a heart rate signal, and is the most faked product on the grey market. Treat this page as a reference for how the two compare, not as advice on which to use.
| Retatrutide | Semaglutide | |
|---|---|---|
| Typical dosage | 1 to 2 mg (starting dose) | 0.25 mg (starting dose) |
| Frequency | once weekly | once weekly |
| Route | Subcutaneous | Subcutaneous, Oral |
| Half-life | About 6 days (phase 1 estimate) | About 7 days (roughly 165 hours) |
| Cycle | ongoing in trials, escalated every 4 weeks toward 4, 8 or 12 mg | ongoing, step up every 4 weeks through 0.5, 1.0, 1.7 and 2.4 mg |
| Research level | Extensively studied | Extensively studied |
| Human trials | Randomized trials | Approved drug |
| Status | Investigational, in Phase 3 trials. Not FDA approved anywhere. | FDA approved as Ozempic, Wegovy and Rybelsus. Compounded and grey-market vials are not approved products. |
| Effects timeline | appetite drop within 1 to 2 weeks, resting heart rate rise in the first month, weight loss builds from about week 4 and was still going at 48 weeks in phase 2 | appetite drops within 1 to 2 weeks, steady weight loss from about week 4 once past 0.5 mg, plateau around 12 to 18 months |
Key differences
Retatrutide vs Semaglutide dosage
Dosage patterns reported in research and community protocols, by goal. Taken from each compound page. Not a prescription.
| Goal | Dosage | Frequency |
|---|---|---|
| Weeks 1 to 4, tolerance | 1 to 2 mg | once weekly |
| Weeks 5 to 8 | 2 to 4 mg | once weekly |
| Weeks 9 to 12 | 4 to 8 mg | once weekly |
| Week 13 onward, if still needed | 8 to 12 mg | once weekly |
| Low-dose hold (common community pattern) | 4 mg | once weekly |
| Goal | Dosage | Frequency |
|---|---|---|
| Weeks 1 to 4, tolerance | 0.25 mg | once weekly |
| Weeks 5 to 8 | 0.5 mg | once weekly |
| Weeks 9 to 12 | 1.0 mg | once weekly |
| Weeks 13 to 16 | 1.7 mg | once weekly |
| Week 17 onward, maintenance | 2.4 mg, or the lowest step that works | once weekly |
Convert any of these to syringe units in the dosage calculator.
Side effects compared
- ▲Nausea, vomiting and diarrhea, rougher than semaglutide in the early weeks
- ▲Resting heart rate up by several beats per minute for the first months
- ▲Skin tingling or heightened skin sensitivity (dysesthesia)
- ▲Constipation and reflux
- ▲Injection site reactions
- ▲Nausea, especially the first few days after each dose increase
- ▲Constipation or diarrhea
- ▲Burping, reflux and early fullness
- ▲Fatigue and low energy from eating less
- ▲Injection site redness or itching
Which should you choose?
Retatrutide fits someone who has exhausted the approved options, including tirzepatide at 15 mg, and accepts grey market sourcing with batch testing. The glucagon component adds energy expenditure and liver fat reduction that semaglutide cannot offer. Nobody should start their GLP-1 experience here. The retatrutide dosage chart covers the trial escalation schedule.
Semaglutide fits people who want the best studied, cheapest and most available drug in the class, or who have cardiovascular disease and want the SELECT data behind them. It also has an oral form for people who will not inject. Follow the 0.25 mg start and 4 week steps in the semaglutide dosage chart; nearly every bad experience comes from going faster.
Semaglutide is the answer for anyone who wants an approved, well understood drug at the lowest price, and the honest answer for most people reading this. Its 15 percent average is less than retatrutide's, but it is a number that millions of people have actually achieved on a product with known contents. Retatrutide will likely be the stronger drug once approved, and the TRIUMPH program suggests the gap is real. The question is whether you want to be an early adopter of an unverified powder with a heart rate signal and no long term safety data to save a year or two of waiting. For someone who has stalled on semaglutide 2.4 mg, the more conservative next step is tirzepatide, which is approved and stronger. Retatrutide comes after that. The retatrutide phase 3 results page tracks what has and has not been published.
Stacking: Not stacked together. Semaglutide is paired with cagrilintide in the CagriSema program; retatrutide has no studied pairing.
Retatrutide is a once-weekly peptide that activates GLP-1, GIP and glucagon receptors together. Phase 2 data showed about 24 percent weight loss at 48 weeks, the largest figure reported for any single compound, but it is still years from approval.
Semaglutide is a once-weekly GLP-1 receptor agonist that cuts appetite and slows digestion, producing average weight loss around 15 percent in trials. It is the molecule behind the Ozempic and Wegovy brand names.
Retatrutide vs Semaglutide: frequently asked
How much more weight do you lose on retatrutide than semaglutide?
Roughly 9 to 13 percentage points more on trial averages: about 24 percent at 48 weeks in retatrutide phase 2 and about 28 percent at 80 weeks in TRIUMPH-1 topline, versus about 15 percent for semaglutide at 68 weeks. No head to head trial has been published and the trials differ in length, so the difference is approximate.
Is retatrutide safer than semaglutide?
No, and it cannot be yet. Semaglutide has years of post approval data and a cardiovascular outcomes trial. Retatrutide has phase 2 and 3 data only, with a resting heart rate increase as its extra signal. The class warnings on thyroid, pancreatitis and gallbladder apply to both.
Can you switch from semaglutide to retatrutide?
People do it, with no trial data to guide them. Community practice is to start retatrutide at the 1 to 2 mg trial dose rather than attempting to match semaglutide milligrams, and to keep each step at 4 weeks. Nausea usually returns during the switch.
Why is retatrutide so expensive compared to semaglutide?
There is no approved product and no competition, so grey market pricing is set by demand and hype. Semaglutide is manufactured at enormous scale and widely compounded. Retatrutide is also the most counterfeited product in the category, so the high price buys no certainty.
What are the retatrutide starting doses?
Phase 3 used 1 or 2 mg weekly, escalated every 4 weeks to 4, 8 or 12 mg. Semaglutide starts at 0.25 mg weekly. The numbers are not comparable across the two drugs; see the retatrutide dosage chart.
Related reading
Weight loss beyond semaglutide alone
Three generations of GLP-1 drugs. What actually separates them?
The triple agonist beats the dual agonist on paper. Is it worth waiting for, or buying early?
The two approved GLP-1 drugs went head to head. What does the result mean for you?
Dosage
Dosage
Sources
- Triple-hormone-receptor agonist retatrutide for obesity, a phase 2 trial. New England Journal of Medicine, 2023
- Once-weekly semaglutide in adults with overweight or obesity (STEP 1). New England Journal of Medicine, 2021
- Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT). New England Journal of Medicine, 2023