Retatrutide · Dosing & maths

Retatrutide dosage: what the research used

Reviewed 22 October 2026 · How we research

This page collects the doses reported in published Retatrutide research and works through the reconstitution maths for common vial sizes. It does not recommend any dose.

Doses used in published research

In the phase 2 obesity trial, participants received once-weekly subcutaneous injections at fixed target doses, reached by stepping up every four weeks:

Trial arm	Starting dose	Target dose	Mean weight change at 48 weeks
1 mg	1 mg	1 mg	−8.7%
4 mg	2 mg or 4 mg	4 mg	−17.1%
8 mg	2 mg or 4 mg	8 mg	−22.8%
12 mg	2 mg	12 mg	−24.2%
Placebo	—	—	−2.1%

These are trial protocol figures under medical supervision — not a recommendation. Phase 3 trials use similar step-ups to target doses of 4, 9 or 12 mg.

Retatrutide reconstitution table

Syringe units (U-100: 100 units = 1 mL) needed for a given amount, by vial size and water volume:

Vial	Water	Concentration	1 mg	2 mg	4 mg
10 mg	1 mL	10 mg/mL	10 units	20 units	40 units
10 mg	2 mL	5 mg/mL	20 units	40 units	80 units
10 mg	3 mL	3.333 mg/mL	30 units	60 units	> 1 mL
15 mg	1 mL	15 mg/mL	6.7 units	13.3 units	26.7 units
15 mg	2 mL	7.5 mg/mL	13.3 units	26.7 units	53.3 units
15 mg	3 mL	5 mg/mL	20 units	40 units	80 units
20 mg	1 mL	20 mg/mL	5 units	10 units	20 units
20 mg	2 mL	10 mg/mL	10 units	20 units	40 units
20 mg	3 mL	6.667 mg/mL	15 units	30 units	60 units

Retatrutide reconstitution calculator

Peptide in vial (mg) Bacteriostatic water added (mL) Amount to measure Syringe

Vial presets:

Concentration—

Volume to draw—

Syringe units (U-100)—

Measurements per vial—

Arithmetic aid for laboratory reconstitution. It does not recommend any amount for any use.

Handling and storage

Reconstitute with bacteriostatic water, adding it slowly down the vial wall and swirling rather than shaking — see the reconstitution guide. Once mixed, refrigerate at 2–8 °C; unmixed lyophilised powder keeps longest frozen (storage guide). Converting between units, mL and mg is covered in syringe units explained.

Retatrutide dosing FAQs

How much bacteriostatic water for a 10 mg Retatrutide vial?

There is no fixed amount — the volume sets the concentration. Adding 2 mL to a 10 mg vial gives 5 mg/mL; 1 mL gives 10 mg/mL, 2 mL gives 5 mg/mL, 3 mL gives 3.333 mg/mL.

How many units is 1 mg of Retatrutide?

At 5 mg/mL (10 mg in 2 mL), 1 mg is 0.2 mL, or 20 units on a U-100 syringe. A different water volume changes this — use the calculator above.

Is there an approved Retatrutide dose?

See the published trial doses above. Any human use of a licensed medicine should follow its prescribing information and a prescriber's advice.

What is a Retatrutide dosage chart?

A table showing how many syringe units a given amount takes at a given concentration. The reconstitution table on this page is one, calculated for 10 / 15 / 20 mg vials.