Retatrutide Testing: How to Tell If Reta Is Real and What a COA Proves

Retatrutide testing means sending a vial to a lab to check 3 things: that it holds retatrutide, how many milligrams are in it, and how pure the peptide is. That tells you whether a vial matches its label. It doesn't tell you the vial is safe to inject. Eli Lilly makes the only genuine retatrutide and says it "cannot be legally sold or marketed for human use," so every vial sold online is someone else's product. And the only regulator lab test of a vial we could find, as of October 2026, found no retatrutide in it at all.

Most of what follows is about the certificate of analysis (COA) a seller or lab hands you. The legal routes to Lilly's drug are in our where to buy retatrutide guide.

Is retatrutide legit, and has it been tested on humans?

The molecule is legit. Retatrutide (Lilly's code LY3437943) is a weekly injection that acts on the GIP, GLP-1 and glucagon receptors, and it has been through every stage of human testing short of approval. Lilly's FAQ, updated in October 2026, says it "has not been reviewed or approved by the FDA or any regulatory agency in the world, and no one can legally sell it for human use." Our is retatrutide legal page covers what that means for buyers.

The products sold online aren't Lilly's. Lilly's August 12, 2026 release counted more than 14,000 websites, ads, posts and listings marketing retatrutide in more than 100 countries.

Here's who has taken part in the 10 Lilly retatrutide trials with reported results that we counted, including placebo and comparison groups. Smaller Phase 1 studies of drug interactions and kidney or liver impairment aren't in it.

That's 8,456 people across 10 trials, 7,720 of them in Phase 3 (our sums of the figures above; Lilly gives no combined total). Everyone on retatrutide in them got Lilly's own product. The results are in our retatrutide clinical trials guide.

What stage of testing is retatrutide in?

Phase 3, the last stage before approval. Lilly has reported 6 positive Phase 3 results, from TRIUMPH-4 in December 2025 to TRANSCEND-T2D-2 on October 28, 2026, the first head-to-head, against Ozempic 2 mg. As of October 2026, TRIUMPH-1 is in the New England Journal of Medicine and TRIUMPH-2 and TRANSCEND-T2D-1 are in The Lancet. TRIUMPH-3, TRIUMPH-4 and TRANSCEND-T2D-2 have no paper yet.

Lilly last said, on September 29, 2026, that it plans to submit retatrutide to the FDA in the first quarter of 2027 as a Biologics License Application (BLA). On October 2, 2026, the FDA decided that retatrutide is a drug, not a biological product, so an application would need to be filed under section 505 of the Federal Food, Drug, and Cosmetic Act. Lilly's appeal on that question is pending in the Seventh Circuit, and we found no ruling as of October 31, 2026 (more on our FDA approval page). TRIUMPH-5, retatrutide against tirzepatide in about 800 adults, is still running.

What retatrutide testing on a COA checks

A COA bundles several tests and covers only the ones somebody paid for.

Purity gets the headline, and it's the least useful number for safety. "99% pure" means 99% of the peptide material is the target peptide; it says nothing about bacterial toxins, which the FDA's March 2026 endotoxin guidance covers.

Health Canada's April 2026 advisory names retatrutide among the peptides it has seized and lists what such products can carry: too much, too little or none of the active ingredient, unlisted ingredients, heavy metals, particles, microbes and endotoxins. A basic COA covers the first and none of the last. For blood work instead, see our is retatrutide safe page.

How to read a retatrutide COA, line by line

Go down this list with your vial in hand and stop at the first failure.

1. Check the lab is a separate business from the seller. A report on the seller's own letterhead is a self-review.
2. Check the date. An old report describes old powder.
3. Match the lot number to the one printed on your vial. If they differ, the report is about somebody else's vial.
4. Read the sample description: the label claim (say, "Retatrutide 10 mg") and how many vials were tested.
5. Look for an identity line saying retatrutide was found. Purity alone doesn't show what the peptide is.
6. Compare the measured amount with the label. It drives the dose math.
7. Look for endotoxin and sterility. If they're missing, nobody checked for bacterial toxins or live germs.
8. Enter the verification code on the lab's website, found by you, not the seller.

Which molecular weight is the lab checking against?

Mass spectrometry compares the measured mass with retatrutide's expected mass. No label prints that number yet, the FDA's substance record flags its own weight as a computed default, and the pages ranking for "retatrutide testing" don't agree. Here's what they listed on September 29, 2026, next to 2 drugs whose labels give one.

They can't all be right, and we won't pick one: no official figure exists to check them against. Our read: an identity result is only as good as the reference it's checked against. Ask the lab what mass or reference standard it used for retatrutide, and be wary of any lab that can't say.

What a short vial does to your dose

Say you mix a vial labeled 10 mg with 2 mL of water and draw 0.4 mL (40 units on a U-100 insulin syringe), expecting 2 mg, the dose everyone in the TRIUMPH trials started on. What you inject depends on what's really in the vial.

A report that gives only "99% purity" leaves every line of that table a guess. Our reconstitution calculator does the water and units math for other vial sizes.

Janoshik reports, and how to check one is real

Janoshik is a lab name that comes up on seller pages and in peptide buyer forums, usually as a report with a verification code. We couldn't check how those reports are produced or shared.

The harder part is confirming a report came from the lab at all. On September 29, 2026, results for "retatrutide janoshik" showed 3 separate domains carrying the Janoshik name. Two listed the same "common GLP-1 peptide blind test," one at $150 and one at $300, and the $150 one gave a Gmail address as its contact. The main janoshik.com site blocked our visit, so we couldn't confirm which sites the lab itself runs. The $150 listing covers identity, amount per vial and purity by HPLC from 1 unopened vial in about 7 business days; endotoxin, sterility, heavy metals and a screen for other peptides are add-ons.

To check a Janoshik report, or any other, reach the lab's site by typing or searching for it yourself, never through a link or QR code the seller sends. Enter the verification code and compare every field: date, sample name, amount, purity and lot. A screenshot or a PDF the seller hosts is unverified.

What testing costs, and what the results show so far

We opened 5 lab and testing listings that ranked for these searches on September 29, 2026 and haven't re-checked them since. Only one priced both endotoxin and sterility testing. The other Janoshik-branded listing charged $300 for the basic test.

Adding endotoxin and sterility to the $150 listing brings one vial to $620, over 4 times the basic test.

The mail-in database in that table publishes results by seller, which makes it the closest thing to a public track record. Its bar is purity of 99.5% or more and an amount within 35% of the label, with no endotoxin check unless someone pays. We haven't re-checked its test counts or pass rate, so we don't quote them. People choose which vials to send, so a pass rate there isn't the share of all vials that pass.

If you're comparing listings for retatrutide for sale, ask for the endotoxin and sterility results by name, for your lot, before you pay. Our retatrutide price page tracks what vials list for, and our retatrutide vendors page covers how to judge a source.

Is retatrutide a scam? What fakes turned out to be

The drug isn't, but some of what's sold under its name has been. These are the cases where a regulator looked:

• Australia's TGA said on September 14, 2026 that a person needed hospital care for uncontrollable vomiting and a torn esophagus after using a product sold as retatrutide. Its lab found no retatrutide, only undeclared semaglutide at about 8 times the level in approved products.
• Victoria's Chief Health Officer reported in June 2026 on 6 cases of acute liver injury since January in people who used products labeled "Retatrutide," "Reta," "R-10" or "R-20." The alert says a contaminant is a possible cause and all such products are at risk. It still listed 6 cases on October 31, 2026.
• The UK's MHRA seized more than 2,000 unlicensed retatrutide and tirzepatide pens at a Northampton site in October 2025, and in May 2026 recovered about 12,000 more doses near Northampton and made 2 arrests.
• Lilly's counterfeit page says federal prosecutors in Florida filed criminal proceedings against someone selling illicit "retatrutide" that, when tested, held a different active ingredient.
• The FDA has sent warning letters to sellers, including Gram Peptides on March 31, 2026 and, on August 24, 2026, a seller of a product called "GLP-3 Reta (Retatrutide)." Both call the products unapproved new drugs.

A COA addresses some of what Lilly's FAQ warns about in illicit products, and only for the batch tested. An identity test run against a real retatrutide reference would have flagged the TGA vial, which held semaglutide, a different molecule. Rules by country are in our availability by country guide.

More red flags beyond the checklist:

• One report reused across batches and months
• Claims of approval, "pharmaceutical grade" or Lilly manufacture, Lilly branding, or a prefilled pen
• A price far below other listings, or no way to reach the seller
• Labels saying the product isn't meant for people, sold with dosing instructions, which the FDA calls a false disclaimer

How a tested vial compares with the legal routes

A verified COA narrows one risk. Here it is next to routes where someone else answers for the product.

Expanded access (NCT07629401) covers adults with a BMI of 35 or more despite the highest available dose of a weight medicine, 2 or more serious obesity-related complications, and no way to join a trial; the treating doctor contacts Lilly. Zepbound prices are for vials or the KwikPen as of October 2026; $449 covers 7.5 mg and up, refilled within 45 days. Trial sites by state are in our retatrutide near me guide.

What a clean report can't tell you

It can't tell you the powder behaves like Lilly's product in your body. Lilly's safety record comes from its own formulation at trial doses. A vial that passes identity, amount and purity hasn't been tested in people, and the report can't show how it was stored or shipped afterward.

We found one peer-reviewed letter on labeling accuracy of products sold as retatrutide in Australia (Piatkowski and colleagues, Drug and Alcohol Review, 2026), but couldn't read its text, so we can't say what it found. Our read: with 6 liver injury cases in one Australian state and a regulator test that found the wrong drug, a verified report that matches your lot and includes endotoxin results is the minimum to ask for, and it still falls short of a trial.

If you'd rather have Lilly's drug than a report about someone else's, the routes are a clinical trial or expanded access through your own doctor, both in our how to get retatrutide guide.