Metabolic and GLP-1

Retatrutide

Approved nowhere, and every vial is off supply chain

What it actually is

Retatrutide is a lab made drug from the company Eli Lilly, taken as a shot under the skin once a week. It works on three of the body's own appetite and blood sugar signals at the same time, and in the company's trials people on the strongest dose lost about a quarter of their body weight. It is not approved for sale in any country, so every vial in anyone's hands came from outside the legal drug supply.

What it is supposed to do

Retatrutide is one molecule that acts on three of the body's own hormone signals at once: glucose dependent insulinotropic polypeptide, glucagon like peptide 1, and glucagon. The effect it is built for is appetite suppression. The three are not pulled evenly, and that is on Lilly's own numbers: in laboratory dishes it acts on the first signal about 8.9 times more strongly than the body's own version does, and less strongly than the natural signal on the other two, so the first one is the loud note.

What people take it for

People take it to lose weight. That is what the company trials measured, and it is what the grey market buying is about: one unreviewed analysis of online discussion up to December 2025 counted 13,589 people describing current use.

The dose question

What circulates: 0.25 to 1.5 mg starting, 4 mg maintenance
What was studied: Up to 12 mg weekly; Lilly phase 2, about a quarter of body weight at the top dose

Trial results describe a molecule, not a vial. No approved version exists at any price, so there is no reference article to hold yours against.

Reported because it is what people use. Nothing here recommends any amount.

How long it lasts

About 6 days, from the published human trial work on the shot given under the skin. That is why the dosing is weekly.

Route studied

Under the skin, once a week, in company trials

Route used

Under the skin, once a week, from unapproved vials

How to check you have the right molecule

No rival molecule is sold under this name, so the check is on the certificate that comes with the vial, and it is the content line rather than the purity line. Purity says what share of the powder is the right substance. Content says how many milligrams are actually in there, and the two can disagree badly: the only public vial test, which the seller paid for, reported 99.76% purity on a 10 mg vial but measured 12.05 mg of drug in it, which is 121% of what the label claimed, on a sample the shop supplied rather than one bought at retail, with no sterility or contamination screen run. No independent published chemical test of grey market retatrutide exists at all. On the nearest similar drug, semaglutide, three vials bought online came back at 7.70% to 14.37% pure against a claimed 99%.

Walked through on two real certificates in how to read a certificate of analysis.

What people get wrong

People assume the dose numbers passed around online came out of the trials. They came out of vial sizes: the trials used 1, 4, 8 and 12 mg a week, while 10 mg is simply one standard vial and 20 mg is two, and 20 mg is two thirds again the highest dose ever given to anyone in a published trial.

What is known about harm

In the company trials the trouble was mostly the gut and it grew with the dose: at the top dose 42.4% of people reported nausea against 14.8% on a dummy shot, 25.3% reported vomiting against 4.8%, and 11.3% quit over side effects against 4.9%. Outside the trials, one published case describes a man who took roughly 40 mg across two days and spent a week with diarrhoea he could not stop, ending in dehydration and kidney damage before he recovered, and the group Public Citizen counted 14 hospitalisations linked to retatrutide in the government adverse event system by June 2026. Nobody has published a chemical test of grey market retatrutide, so what is actually inside a bought vial has not been measured.

The arithmetic

Retatrutide is sold in 10 mg, 12 mg, 24 mg, 30 mg and 60 mg vials. Mixing errors put people an order of magnitude off using a perfectly good vial, and the arithmetic is simple enough to check yourself.

Vial	Water	Concentration	In 10 units
10 mg	1 mL	10 mg/mL	1 mg
10 mg	2 mL	5 mg/mL	500 mcg
10 mg	3 mL	3.33 mg/mL	333 mcg
12 mg	1 mL	12 mg/mL	1.2 mg
12 mg	2 mL	6 mg/mL	600 mcg
12 mg	3 mL	4 mg/mL	400 mcg
24 mg	1 mL	24 mg/mL	2.4 mg
24 mg	2 mL	12 mg/mL	1.2 mg
24 mg	3 mL	8 mg/mL	800 mcg
30 mg	1 mL	30 mg/mL	3 mg
30 mg	2 mL	15 mg/mL	1.5 mg
30 mg	3 mL	10 mg/mL	1 mg
60 mg	1 mL	60 mg/mL	6 mg
60 mg	2 mL	30 mg/mL	3 mg
60 mg	3 mL	20 mg/mL	2 mg

10 units is 0.1 mL on a U-100 insulin syringe, whatever is in it. For any other combination, or to see the arithmetic worked out, use the calculator.

Everything on this page is a summary. The citations, the studies and the reasoning live in the full entry.

Read the full entry on Retatrutide

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