Question 1

What is the retatrutide dosing schedule?

Accepted Answer

There is no approved retatrutide dosing schedule. In the published phase 2 obesity trial, target doses were 1, 4, 8 or 12 mg once weekly; groups assigned 4 mg or more began at 2 mg or 4 mg and escalated every 4 weeks for up to 12 weeks. Phase 3 trials used protocol-defined escalation under medical supervision. Those are trial designs, not instructions for using a retail vial.

Question 2

How much bacteriostatic water do I add to 10 mg of retatrutide?

Accepted Answer

It depends entirely on what you want your draw to read. 1 mL gives 10 mg/mL, so 1 mg sits at 10 units on a U-100 barrel. 2 mL gives 5 mg/mL and 20 units per mg. 3 mL gives 3.33 mg/mL and 30 units per mg. None is more correct than another — the water only sets the concentration, never the dose. Use the “I want N units” mode above to solve it backwards from a number you can read on your syringe.

Question 3

How do I reconstitute a 30 mg retatrutide vial?

Accepted Answer

The same arithmetic, three times as concentrated. 30 mg in 1 mL is 30 mg/mL, so a milligram is only 3.3 units — far too coarse to read. 30 mg in 3 mL is 10 mg/mL and 10 units per mg, which is about as dilute as a standard 3 mL vial will allow. A 30 mg vial therefore forces a concentrated solution and small draws, which is the practical argument against buying the biggest vial. Add the water down the side of the vial rather than onto the powder, and swirl rather than shake.

Question 4

How many mL is a retatrutide dose?

Accepted Answer

There is no answer to that question until you say what concentration your vial is, because millilitres measure volume and a dose is a mass. Divide the milligrams you want by the milligrams per millilitre in your vial. At 5 mg/mL each milligram is 0.2 mL, or 20 units. At 10 mg/mL each milligram is 0.1 mL, or 10 units. This site does not publish a retatrutide dose to put in the syringe: no regulator has approved one, and the figures that appear in the phase 2 trial are trial protocol doses under medical supervision, not a schedule anyone should copy.

Question 5

Is retatrutide legal to buy?

Accepted Answer

It is not approved for human use anywhere in the world, and it is not lawfully sold for human use anywhere. The FDA has issued warning letters to sellers, and has stated explicitly that marking a vial “research use only” or “not for human consumption” does not exempt it when the seller's own marketing establishes that it is intended for people. Selling bacteriostatic water alongside the vials has itself been treated by the FDA as evidence of that intent.

Question 6

What is retatrutide's half-life?

Accepted Answer

Roughly 6 days. The phase 1 study reported a terminal half-life of 5 to 7 days, which is what supports once-weekly dosing in the trials.

Retatrutide Reconstitution and Dosage Calculator

Investigational — not approved in any country

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Key facts

Doses used in published studies

How good is the evidence?

Retatrutide dosage chart: what the trials actually did

Why there is no such thing as compounded retatrutide

Common questions

Sources