Retatrutide
An investigational triple agonist from Eli Lilly that hits the GLP-1, GIP, and glucagon receptors at once. People watch it for the largest weight loss yet seen in obesity trials, with phase 2 reaching roughly 24% of body weight over 48 weeks.
Where to buy Retatrutide, cheapest first.
Prices from 3 vendors across the market. We link straight to each vendor’s product page and grade vendors on public lab data, so you’re not just chasing the lowest number.
What Retatrutide actually does.
The simple version first, then a little more for the curious. No biochem degree required.
It pushes three appetite and metabolism switches together, turning down hunger while turning up energy burn, which is why the weight loss numbers run higher than single or dual agonists.
How it works
Retatrutide is a 39-amino-acid peptide that activates three receptors at once: GLP-1 and GIP, which boost insulin after meals and slow digestion so you feel full, and glucagon, which increases energy expenditure and fat burning. That third arm is what sets it apart from semaglutide and tirzepatide.
Where it acts
It works through the gut-brain-pancreas axis and the liver. GLP-1 and GIP calm appetite and steady blood sugar, while glucagon agonism nudges the liver and metabolism to spend more energy. The combined effect is less intake and more output at the same time.
What people notice
In trials, appetite drops sharply and weight comes off faster than with earlier agonists. Effects build over weeks as the dose is titrated up. The trade-off is more gastrointestinal upset, especially nausea, during each dose step.
Honest caveat: the human data here is genuinely strong by peptide standards, with published phase 2 and reported phase 3 obesity trials, but Retatrutide is still investigational and not approved anywhere. It is sold strictly for research use only, and what vendors ship is not the studied pharmaceutical product. None of this is medical advice, talk to a licensed provider before starting anything.
How to take it.
Retatrutide is a once-weekly subcutaneous injection into the fat with a tiny insulin needle, the same way semaglutide and tirzepatide are run. It is not an oral peptide, so the injectable form is what people use. The routine is below; for titration and timing, see the full guide.
Reconstitute the vial
Add bacteriostatic water down the side of the vial (a 10mg vial + 1mL = 10mg/mL). Let it dissolve. Swirl gently, don't shake.
Draw your dose
On a U-100 insulin syringe, pull to your unit mark. 2mg at 10mg/mL is 20 units (0.2mL). Use the calculator if you're unsure.
Pinch and inject
Swab with alcohol, pinch a bit of fat, insert at 45–90°, push slowly. Subcutaneous into the belly is simplest. Inject the same day each week.
Rotate your sites
Move to a different spot each week so no area gets sore or lumpy. Store the vial in the fridge between doses.
The easiest spots are the belly (about 2 inches either side of the navel), the love handles, the front of the thigh, and the back of the upper arms. Rotate every injection.
Don't do the math, let the calculator do it.
This is Retatrutide's typical setup, already worked out. Change any value and the draw updates instantly.
Typical Retatrutide dose: started low at 2 mg once weekly and titrated up every 4 weeks, stepping through 4 mg and 8 mg toward target doses of 8 to 12 mg once weekly. It is escalated slowly to limit nausea, not jumped straight to the top.
Cycling Retatrutide.
Whether Retatrutide is cycled at all, how long people run it, and the honest reasoning behind it.
Titrated up over weeks; not cycled.
Retatrutide is not really cycled the way a recovery peptide is. It is a weight loss compound, so the pattern that mirrors the trials is a long, steady run: titrate up over the first months, then hold a maintenance dose for as long as the weight loss goal is active.
The honest catch is what happens when you stop. Like other GLP-1 drugs, appetite tends to return when the compound is discontinued, and some weight regain is common without lasting diet and activity changes. This is a long-game tool, not a short blast.
- Ramp slowly through the titration steps rather than jumping to a high dose, which only worsens nausea.
- Hold a maintenance dose once you reach a level that balances results and side effects, often 8 mg.
- Plan for the off-ramp. Appetite and some weight tend to come back after stopping, so a tapering plan and lifestyle changes matter. This is a conversation for a licensed provider.
Want the full picture, on and off periods, the washout, stacking, and keeping your results? Read how peptide cycling works →
What's actually in the vial.
For 2 of these vendors we link the per-batch certificate itself (a specific lab report, COA PDF, or certificate image), and the purity below is read straight off that certificate. The rest link to the vendor's general lab-results page. We don't run the labs ourselves and we don't show a purity number unless it's printed on a certificate we link, so you can open the document and check it against the batch yourself.
| Vendor | Purity (per COA) | Batch / report | Certificate |
|---|---|---|---|
| Onyx Biolabs | 98.771% | RET40-26051A | View COA ↗ |
| Pure Rawz | 98.2% | R5T04 | View COA ↗ |
What people pair it with.
Retatrutide is potent enough that most people run it on its own. When it is combined, the goal is usually to blunt side effects or preserve muscle, not to stack more agonists on top.
Appetite & satiety
Some researchers pair the triple agonist with the amylin analog cagrilintide to push satiety further. This is experimental layering, not an established protocol, and it raises the side-effect load.
View stack →Tolerability support
BPC-157 is sometimes added in the hope of easing the gut upset that comes with dose escalation. Evidence for this is anecdotal, so treat it as unproven.
View stack →Standard approach
The most common and most evidence-aligned way to run it. The trials used it as a single agent with slow titration, and that is what the data actually supports.
View stack →In the same corner.
Other weight and metabolic peptides people compare against Retatrutide.
Questions, answered straight.
Is Retatrutide legal?
Retatrutide is not approved as a medicine anywhere in the world. The vendors we compare offer it strictly for research use only, not for human use. It is also banned by WADA under the non-approved substances category, so competing athletes should steer clear. Rules vary by country, so check what applies where you are.
What does research use only actually mean?
It means the product is sold for laboratory and research purposes, not as a supplement or medicine for people. It has not been reviewed or approved for human use by the FDA, and the FDA has warned compounders about selling it. We aggregate prices and public lab data so you can see the landscape; what you do with that is between you and a licensed provider.
How do I store it?
Keep the sealed, freeze-dried vial in the fridge and out of direct light. Once you mix it with bacteriostatic water, store it refrigerated and use it within a few weeks. Don't freeze a reconstituted vial.
How is it dosed?
Trials started at 2 mg once weekly and titrated up every 4 weeks through 4 mg and 8 mg toward 8 to 12 mg weekly. The slow ramp is what keeps nausea manageable. Use the calculator to turn your vial and dose into exact units.
How is it different from tirzepatide?
Tirzepatide hits two receptors, GLP-1 and GIP. Retatrutide adds a third, glucagon, which raises energy expenditure on top of appetite suppression. In trials that third arm is associated with larger weight loss, but also more gastrointestinal side effects.