Retatrutide Dosing Calculator
Turn milligrams into syringe units. Pick your vial size, how much bacteriostatic water you add and the amount per injection. The calculator shows exactly where to draw to on a U-100 insulin syringe.
Once weekly, this vial lasts about 5 weeks.
Units for common amounts at your concentration
| Amount | Units (U-100) | Volume | Amounts per vial |
|---|
How the retatrutide calculator works
The maths is the same for any lyophilised peptide:
- Concentration = mg in vial ÷ ml of water. A 10 mg vial + 2 ml = 5 mg/ml.
- Volume to draw = amount (mg) ÷ concentration. 2 mg ÷ 5 mg/ml = 0.4 ml.
- Units = volume × 100 on a U-100 syringe. 0.4 ml = 40 units.
If the units come out very small (under ~5), add more water so small amounts are easier to measure. If they exceed your syringe, use less water or a larger syringe.
Retatrutide doses used in clinical trials
For reference only. These are supervised trial protocols as published, not advice:
| Trial | Once-weekly doses studied | Titration | Mean weight change |
|---|---|---|---|
| Phase 2 (NEJM, 2023) | 1, 4, 8, 12 mg | Start 2 mg (or 4 mg), stepped up every 4 weeks | Up to −24.2% at 48 weeks (12 mg) |
| TRIUMPH-4 (Phase 3) | 9, 12 mg | Gradual escalation | −26.4% / −28.7% at 68 weeks |
| TRIUMPH-1 (Phase 3) | 4, 9, 12 mg | Gradual escalation | −19.0% / −25.9% / −28.3% at 80 weeks |
| TRIUMPH-2 (Phase 3, T2D) | 4, 9, 12 mg | Gradual escalation | −12.7% / −19.1% / −20.8% at 80 weeks |
The most common side effects in trials were nausea, diarrhoea, constipation and vomiting, mostly during dose escalation. Abnormal skin sensations (dysaesthesia) were also reported. See ourPhase 3 results breakdown for detail.
Need a vial?
Our #1-ranked UK supplier, LeoLab, stocks retatrutide from 10 mg to 60 mg (from £75, checked 9 October 2026) and publishes a mixing guide for each size. Compare all sizes on the retatrutide price UK page.
FAQ
How many units is 2 mg of retatrutide?
It depends on the reconstitution. A 10 mg vial mixed with 2 ml of bacteriostatic water gives 5 mg/ml, so 2 mg is 0.4 ml, or 40 units on a U-100 insulin syringe. With 1 ml of water (10 mg/ml), 2 mg is 20 units.
How much bacteriostatic water should I add to a retatrutide vial?
There is no single correct amount. More water makes each unit carry less retatrutide, which makes small amounts easier to measure accurately. Many guides use 1–3 ml for a 10 mg vial. The calculator shows how each choice changes the units you need to draw.
How many doses are in a 10 mg vial of retatrutide?
Divide the vial content by the amount per injection: a 10 mg vial holds five 2 mg amounts, two-and-a-half 4 mg amounts, and so on. The calculator works this out for any vial size.
What doses were used in retatrutide clinical trials?
In the Phase 2 trial (NEJM, 2023), once-weekly doses of 1–12 mg were studied, with gradual escalation every 4 weeks starting at 2 mg. Phase 3 TRIUMPH trials use maintenance doses of 4 mg, 9 mg and 12 mg once weekly. These are trial protocols under medical supervision, not recommendations.