Retatrutide is reconstituted the same way as other GLP-1 peptides — add bacteriostatic water to the freeze-dried powder.
Vials are commonly 5–30 mg; the water volume you add sets the concentration, never the total amount of compound.
Concentration = vial mg ÷ water mL. Adding 2 mL to a 10 mg vial gives 5 mg/mL.
Correctly mixed retatrutide is clear and colourless with no visible particles.
Add water down the wall, swirl gently (never shake), label with concentration and date, and refrigerate.
To reconstitute retatrutide, add bacteriostatic water to the freeze-dried powder — the same method used for other GLP-1 peptides such as semaglutide and tirzepatide. Retatrutide is supplied as a lyophilised (freeze-dried) powder in vials that are commonly 5 mg to 30 mg; the volume of water you add sets the concentration, and nothing else changes the amount of compound in the vial.
What retatrutide is
Retatrutide (LY3437943) is an investigational triple GIP / GLP-1 / glucagon receptor agonist studied for weight loss and given once weekly in clinical trials1. It arrives as a dry powder that has to be reconstituted before it can be drawn into a syringe.
The one formula
concentration = milligrams in the vial ÷ millilitres of water added. In plain terms: the water is just the carrier. It decides how concentrated the solution is — and therefore how many units a given amount occupies on the syringe — but it never changes the total milligrams you started with.
How much BAC water for a retatrutide vial
Any volume works; it only sets the concentration. This table shows the concentration you get at common bacteriostatic-water volumes for the vial sizes people ask about most:
Vial
+ 1 mL
+ 2 mL
+ 3 mL
5 mg
5 mg/mL
2.5 mg/mL
1.67 mg/mL
10 mg
10 mg/mL
5 mg/mL
3.33 mg/mL
12 mg
12 mg/mL
6 mg/mL
4 mg/mL
15 mg
15 mg/mL
7.5 mg/mL
5 mg/mL
20 mg
20 mg/mL
10 mg/mL
6.67 mg/mL
30 mg
30 mg/mL
15 mg/mL
10 mg/mL
A common choice is a round concentration that makes draws easy to read — for example, 2 mL into a 10 mg vial gives 5 mg/mL. Enter your own vial size and water volume in the retatrutide calculator to see the exact draw in syringe units.
Method
Bring the vial and bacteriostatic water to room temperature; swab both stoppers.
Add your chosen water volume down the inside wall of the vial. Bacteriostatic water contains a preservative (0.9% benzyl alcohol) that lets you re-enter the vial over the days that follow2.
Swirl gently — never shake. Give it a few minutes to dissolve fully.
Label the vial with its concentration and the date, and refrigerate.
No — the method is identical to reconstituting tirzepatide: a freeze-dried powder plus bacteriostatic water. The only practical difference is the vial sizes and concentrations you are likely to work with.
Try it with the calculator
CONCENTRATION
10 mg/mL
YOUR DRAW (U-100)
40 units
DOSES IN VIAL
5
0102030405060708090100
Frequently asked
How much BAC water for a 10 mg retatrutide vial?
Any volume works — it sets the concentration, not the amount of compound. Adding 2 mL of bacteriostatic water to a 10 mg vial gives 5 mg/mL; 1 mL gives 10 mg/mL. Pick a volume that makes your draw easy to read and match it in the calculator.
How much BAC water for a 30 mg retatrutide vial?
A 30 mg vial reaches 10 mg/mL with 3 mL of bacteriostatic water, or 15 mg/mL with 2 mL. Larger vials simply reach higher concentrations at the same water volume.
How do you mix retatrutide with bacteriostatic water?
Bring both to room temperature, swab the stoppers, add the water down the inside wall of the vial, swirl gently (never shake), then label with the concentration and date and refrigerate.
Is retatrutide reconstituted like tirzepatide?
Yes — the method is identical. Both arrive as a freeze-dried powder that is reconstituted with bacteriostatic water; only the common vial sizes and concentrations differ.
References
Jastreboff AM, Kaplan LM, Frías JP, et al. Triple–hormone-receptor agonist retatrutide for obesity — a phase 2 trial.N Engl J Med. 2023. DOI 10.1056/NEJMoa2301972
Pfizer Injectables / U.S. Pharmacopeia Bacteriostatic Water for Injection, USP — prescribing information (0.9% benzyl alcohol added as a bacteriostatic preservative; multiple-dose container).DailyMed (U.S. National Library of Medicine). 2023. Bacteriostatic Water for Injection USP
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