What is retatrutide?
Retatrutide is an experimental obesity drug from Eli Lilly that has produced the largest weight loss ever recorded in a major trial, and that you cannot yet buy. It’s a once-weekly injection, and its headline feature is that it activates three hormone receptors: GIP, GLP-1, and glucagon. The approved drugs in this class hit one or two.
It is not FDA approved. Retatrutide is still working through late-stage (Phase 3) clinical trials, which means the only lawful way to receive it today is by joining one of those trials. Everything below describes what the research shows so far, not a product you can pick up at a pharmacy.
How does retatrutide work?
Retatrutide acts on three receptors at once, where semaglutide acts on one and tirzepatide on two. That third target is the story behind its trial numbers.
- GLP-1, which reduces appetite and prompts insulin after meals. This is the pathway behind every drug in the class.
- GIP, the second receptor tirzepatide added.
- Glucagon, which is the genuinely new one here.
The first two mostly reduce how much you eat, which is where the weight loss in approved GLP-1 drugs comes from. The glucagon receptor is proposed to work on the other side of the equation, energy expenditure rather than intake. That mechanism has not been established for this drug in our evidence base, so treat it as the rationale behind the trials rather than a demonstrated effect.
Some coverage nicknames it a “GLP-3.” That is not a drug class. Retatrutide belongs to the broader GLP-1 drug class, alongside tirzepatide and semaglutide.
Receptors it activates
Triple agonist · GLP-1 + GIP + glucagon
- GLP-1
Curbs appetite and triggers insulin after meals
- GIP
Amplifies the insulin response and how the body handles fat
- glucagon
Lifts energy expenditure, so the body burns more
Retatrutide approval timeline & clinical trials
Retatrutide is in Phase 3, the final stage before a company can ask the FDA to approve a drug. Lilly’s Phase 3 program is called TRIUMPH, and its studies in obesity (TRIUMPH-1) and obesity with knee osteoarthritis (TRIUMPH-4) are the ones to watch.
| Trial | Dose | Duration | Avg. weight loss | Studied in |
|---|---|---|---|---|
| Phase 2 (obesity) | 12 mg | 48 weeks | 24.2% (~58 lb) | Adults with obesity, no diabetes |
| TRIUMPH-1 | Up to 12 mg | 80 weeks | ~24% | Adults with obesity (Phase 3) |
| TRIUMPH-4 | Up to 12 mg | 80 weeks | ~26% (~64 lb) | Obesity with knee osteoarthritis (Phase 3) |
When could it be approved? There is no confirmed date, and as of August 2026 there is still no approved FDA application for retatrutide. We checked FDA’s own approvals database directly rather than relying on secondary reporting.
Approval would require two things that have not happened: Lilly completing and reporting the Phase 3 program, then submitting an application the FDA reviews, which itself takes months. Estimates circulate, and they move with each readout. Treat any firm date you see, including ones we may have published previously, as an estimate rather than a schedule.
How much weight can you lose on retatrutide?
In its 48-week Phase 2 trial, adults with obesity lost an average of about 24 percent of body weight at the highest 12 mg dose, roughly 58 lb, against about 2 percent on placebo. That is the largest average weight loss reported for an obesity medication, and it is the figure driving the attention.
Read that figure differently from the ones on our approved-drug pages. Every number on those pages comes from an FDA label or a graded claim in our evidence base. Retatrutide has neither, because it is not approved and there is no label. The figure above comes from the published Phase 2 paper listed in our sources, and we have not yet put that paper through our own evidence review.
Three caveats matter. This is Phase 2 data, and Phase 3 results can shift it. Retatrutide has never been compared head to head against tirzepatide or semaglutide, so any “roughly double” framing is a cross-trial comparison rather than a direct one, and cross-trial comparisons in this class are explicitly treated as indirect. And as with every trial in this class, the figure is a group average measured on top of structured lifestyle support, not a result the drug produced alone.
What are the side effects of retatrutide?
Because retatrutide hasn’t finished Phase 3, its side-effect profile is not yet fully established, an important difference from approved drugs. What’s been reported so far looks like the rest of the GLP-1 class, plus one thing to watch.
Common · usually temporary
- Nausea reported
- Diarrhea reported
- Vomiting reported
- Constipation reported
- Increased heart rate dose-related
Serious · call your provider
- Not yet fully characterized, retatrutide has not completed Phase 3 safety review
- GI effects typical of the GLP-1 class (pancreatitis risk under study)
- Dose-dependent increases in heart rate observed in trials
- Long-term safety is unknown until trials conclude
Who should not take retatrutide?
Because retatrutide isn’t approved, “who should not take it” isn’t really a prescribing question, there’s no prescription to write. In practice it comes down to two things: who clinical-trial investigators screen out, and who should steer clear of the grey-market product being sold in retatrutide’s name.
Do not take retatrutide if…
- You or a close family member has had medullary thyroid carcinoma (MTC) or MEN 2, the standard exclusion for this drug class
- You've had a serious allergic reaction to an incretin or GLP-1 medication
- You're considering buying retatrutide from a research-chemical or grey-market seller, these products are unapproved, unregulated, and illegal to sell for human use
Talk to your provider first if…
- You've had pancreatitis, gallbladder disease, or gallstones
- You have kidney disease or a history of dehydration
- You take insulin or a sulfonylurea (higher risk of low blood sugar)
- You're pregnant, planning to be, or breastfeeding
- You have type 1 diabetes
The cautions above are the factors trial investigators weigh when deciding who can safely enroll, not a green light to source retatrutide elsewhere. Until Phase 3 finishes and the FDA reviews the data, a supervised clinical trial is the only setting where anyone should be taking it.
Retatrutide dosage in trials
Retatrutide has no FDA-approved dose, it isn’t approved. In trials, it’s been given once weekly and escalated slowly, much like tirzepatide, up to a 12 mg maximum. The schedule below is drawn from the trial protocols and is shown for context only, not as instructions.
| Dose | When | Notes |
|---|---|---|
| 2 mg | Trial starting dose | Investigational, schedule set by trial protocol, not an FDA label |
| 4 mg | Escalation | Stepped up monthly in trials |
| 8 mg | Escalation | Mid-range dose studied |
| 12 mg | Highest studied | Produced the largest weight loss in Phase 2 |
How much will retatrutide cost?
There’s no price yet, retatrutide isn’t approved, so Lilly hasn’t set one. Any figure quoted today is guesswork at best and a grey-market red flag at worst: a drug you can’t legally buy can’t have a legitimate price. What we can do is set expectations from the drugs it would compete with.
If retatrutide launches in line with its sibling drugs, expect a list price in the same ballpark as tirzepatide and semaglutide, roughly $1,000–$1,350 a month before insurance, with what you’d actually pay depending on coverage, savings programs, and whether it’s approved for weight loss, diabetes, or both. None of that is settled, and insurance coverage for a brand-new obesity drug typically lags approval by months or years.
If cost matters now, the practical move is to price out a drug you can actually get today, see alternatives available now below, and our cheapest GLP-1 options.
Counterfeit & grey-market retatrutide
This is the most important section on the page, so here is the blunt version: if you can buy something labeled “retatrutide” today, it is not an FDA-approved product. Retatrutide is available legally only through Lilly’s clinical trials. A grey market has grown around the trial results anyway, selling “research peptides,” powders and pre-filled pens.
One trap is worth naming specifically. Retatrutide-labelled products do appear in public drug databases, listed by commercial registrants under invented brand names. A database listing is not an approval. When we checked FDA’s approvals database in August 2026 it returned no approved application for retatrutide, while a separate drug-listing database carried multiple retatrutide entries submitted by an overseas e-commerce registrant. If you find a product page and conclude the drug must therefore be approved, that inference is wrong.
A related hazard applies to anything sold as a powder or in a vial rather than a pen: it is often dosed in units rather than milligrams, which has produced real measurement and concentration errors with compounded GLP-1 products.
The tell is simple: any website or individual offering to sell you retatrutide is, by definition, not legitimate, because no legitimate retatrutide product exists to sell.
How to get retatrutide legally
There’s exactly one lawful path today, a clinical trial, plus a sensible plan B if you want to start losing weight now with a drug you can actually get.
Join a clinical trial
- Search ClinicalTrials.gov for active retatrutide (TRIUMPH) studies recruiting near you.
- Read the eligibility criteria carefully, trials screen on BMI, health conditions, and location, and some assign you to placebo.
- Apply and complete screening through the study site; a trial clinician determines whether you qualify.
Alternatives available now
If you don’t want to wait for approval, the approved triple- and dual-agonist landscape already offers powerful options, and a licensed provider can start you on one this week.
1
Through your doctor
Any prescriber can write a GLP-1 medication. Bring your insurance details, since coverage often requires prior authorization, and your doctor's office handles that paperwork.
2
Through telehealth
Licensed online clinics evaluate you remotely and, if appropriate, prescribe a GLP-1 medication or a tirzepatide or semaglutide-based program, usually within a few days.
3
Pharmacy + savings
Prescriptions fill at regular pharmacies or the maker's direct program. Check the manufacturer savings card before paying list price.
Telehealth options we've reviewed
All provider reviewsNo legitimate a GLP-1 medication without a prescription. Sellers offering it with no medical review are operating outside the law, and counterfeit pens are common. Stick to licensed providers and pharmacies. Important safety information
We're independent: we don't sell medication. Some links may earn us a commission at no cost to you; it never affects what we recommend. Prices change often, so always confirm with the provider.
Retatrutide vs tirzepatide and semaglutide
On the numbers, retatrutide leads, but it’s the only one of the three you can’t get. Tirzepatide is the most powerful approved option today.
| Attribute | Retatrutide | Tirzepatide |
|---|---|---|
| Active ingredient | retatrutide | tirzepatide |
| Sold as | – | Mounjaro · Zepbound |
| Receptors targeted | Triple: GIP · GLP-1 · glucagon | Dual: GIP · GLP-1 |
| How it’s taken | – | Weekly injection |
| FDA-approved for | Not yet approved | Type 2 diabetes · Weight management & sleep apnea |
| Avg. weight loss in trials | ~24% | ~21% |
| List price (before insurance) | – | ~$1,060–$1,070/mo |
| Maker | Eli Lilly | Eli Lilly |
Retatrutide vs Tirzepatide
Retatrutide adds a third receptor (glucagon) and posted larger trial numbers, but tirzepatide is approved and available today, retatrutide isn't.
Retatrutide myths and misconceptions
No drug in this space attracts more hype, or more grey-market noise, than retatrutide. Here’s what’s actually true behind the five claims we hear most.
Myth You can buy real retatrutide right now.
You can't. Retatrutide is investigational, the only lawful way to receive it is through a clinical trial. Anything sold online as retatrutide is unapproved grey-market product, not the tested drug.
Myth Retatrutide is approved, or certain to be approved soon.
It isn't approved, and approval isn't guaranteed. Phase 3 trials are still ongoing, and the timing depends on those results and FDA review, treat any firm date as an estimate.
Myth Retatrutide is just a stronger Ozempic.
It works differently. Ozempic (semaglutide) hits one receptor; retatrutide is a triple agonist targeting GIP, GLP-1, and glucagon, a distinct mechanism, not simply a higher dose.
Myth The Phase 2 weight-loss numbers are final.
They're early. Phase 3 trials are larger and longer, and results can shift the averages up or down. The headline figure comes from Phase 2 and isn't the last word.
Myth Grey-market research-chemical versions are equivalent to the real drug.
They aren't. These products have unverified purity, dose, and safety, no one is checking what's in the vial, so there's no way to know you're getting real, correctly dosed retatrutide.