Retatrutide is one of the most searched compounds in the research-peptide market, and "how to reconstitute retatrutide" is a question with no official answer. There is no approved product, so there is no label; the trial registrations do not describe the formulation; and the only FDA listings that exist are for bulk powder. What a person searching this finds instead is vendor instructions. This page reports what the record contains, sets out the concentration arithmetic in the third person, and explains why the arithmetic is only as good as the number printed on the vial. It is not an instruction to prepare or use anything. How brands appear on this site is set out on our disclosure page.
What the record contains
No label. Drugs@FDA holds no application for retatrutide and openFDA's label endpoint returns nothing for it, read 2026-09-23. A label is where a regulator fixes the diluent, the volume, the concentration and the in-use period after reviewing stability data. For retatrutide none of those four has been fixed by anyone.
A silent trial record. Lilly's phase 2 obesity trial (NCT04881760) and its phase 3 TRIUMPH master protocol (NCT05929066) describe the intervention in two words: "Administered SC". Neither registration says whether trial participants used a vial, a pen or a prefilled syringe, or at what concentration. Whatever the trials used, it is not described in the public record, and nothing suggests it involved anyone mixing powder at home.
Bulk-powder listings. FDA's NDC directory, queried through openFDA on 2026-09-23, held 12 retatrutide listings. All 12 are "BULK INGREDIENT" powder, from seven labelers — Hybio, Shanghai SynTheAll, Qingdao Biopeptek, Shenzhen Alvantis, Harbin Jixianglong, Sinopep-Allsino and Eternal Wealth (China) — in packages from a 1 g bottle to a 7 kg drum. A bulk listing records that a firm told FDA it makes an ingredient. It is not an approval, and it is not a finished product anyone is meant to inject. Our research-use-only explainer covers what that label does and does not mean.
The procedure, as labels for other products describe it
With no retatrutide label, the nearest official description of the procedure is the label of an approved lyophilized peptide. EGRIFTA WR's label, for example, specifies the exact diluent volume, says to swirl rather than shake, to inspect for particles, and to discard seven days after mixing. Our general reconstitution page sets out those steps as that label states them. They describe how the procedure is done for that product; none of the numbers transfers to retatrutide.
The arithmetic
The arithmetic is the same for every lyophilized peptide: milligrams in the vial ÷ millilitres of diluent = mg/mL, and one unit on a U-100 insulin syringe is 0.01 mL. Applied to the arms Lilly's phase 2 trial ran, which are set out with their escalation paths on our retatrutide dosage page:
| Trial arm amount | 10 mg vial, 2 mL (5 mg/mL) | 20 mg vial, 2 mL (10 mg/mL) | 20 mg vial, 1 mL (20 mg/mL) |
|---|---|---|---|
| 1 mg | 20 units | 10 units | 5 units |
| 2 mg | 40 units | 20 units | 10 units |
| 4 mg | 80 units | 40 units | 20 units |
| 8 mg | 160 units | 80 units | 40 units |
| 12 mg | 240 units | 120 units | 60 units |
Three things follow from the table, and they are arithmetic, not advice. The same milligram amount is four different unit figures in four columns, so a unit number copied from a source that used another vial or volume is wrong by the ratio of the two concentrations. Above 4 mg, the lowest concentration outruns a standard syringe: 8 mg is 160 units and 12 mg is 240, more than one 100-unit syringe holds. And at 12 mg a 10 mg vial is not enough for one amount, whatever the volume. Medibact Guides' retatrutide reconstitution page carries the full water-volume grid for the common vial sizes.
The number the arithmetic starts from
Every figure in that table assumes the vial holds exactly what its label says. That is the least-verified number in the whole calculation.
Finnrick, a site that publishes laboratory results for research peptides, listed on 2026-09-23 3,858 retatrutide tests across 293 vendors since December 2024. Of the most recent 200 shown on its public page, 142 passed, 54 failed and 4 were incomplete under its "purity focus" standard, which requires 99.5 percent purity and a measured quantity within plus or minus 35 percent of the label. This page reports those counts and does not name any vendor or judge any result; how that site gathers its samples is compared with five others on our page on who tests peptide vendors.
What the tolerance means in arithmetic: a vial labelled 10 mg that sits anywhere inside a ±35 percent band holds between 6.5 and 13.5 mg. Mixed with 2 mL and drawn to 80 units, the calculated "4 mg" is anywhere from 2.6 to 5.4 mg. A vial outside the band is further off still. The difference between purity (a ratio within the peptide fraction) and content (how much peptide is in the vial) is explained on our peptide testing page; a certificate that reports only purity does not answer the question this arithmetic depends on.
Storage after mixing
No stability study of retatrutide in solution has been published, and no label sets an in-use period. Refrigerated periods of several weeks appear on vendor and forum pages; they are commonly cited figures, not measurements for this molecule. What approved products show is how product-specific the answer is: EGRIFTA WR's in-use limit is seven days at room temperature in the bacteriostatic water supplied with it. What the labels say about solutions in general is on our peptide storage page. Retatrutide's sibling tirzepatide does have a label, and every product on it is sold already dissolved — see how the tirzepatide label handles concentration.
What is not known
The formulation Lilly used in its trials; retatrutide's stability in bacteriostatic or sterile water; its compatibility with any particular diluent; and, for any given research vial, how much retatrutide it actually contains until a content assay says so. Nothing on this page is a recommendation, and retatrutide buy-intent questions — where it is sold, by whom, at what price — are outside what it covers.
Sources and dates
Read 2026-09-23: Drugs@FDA and the openFDA drug label endpoint (no retatrutide records); openFDA NDC directory, 12 retatrutide listings; ClinicalTrials.gov records NCT04881760 and NCT05929066; Finnrick's public retatrutide page and methodology page; the EGRIFTA WR label as summarised on our reconstitution page. Corrections go to the contact page.