Retatrutide Dosage Calculator
Calculate exact retatrutide injection volumes for any dose. Uses standard reconstitution formulas — pre-filled for a 10mg vial.
Retatrutide is a triple GIP, GLP-1, and glucagon receptor agonist in late-stage clinical trials — the first compound to target all three metabolic receptors simultaneously. Phase 2 data showed 24.2% average weight loss at 48 weeks (Jastreboff et al., NEJM 2023 — see source below) — above reported results for semaglutide and tirzepatide in separate trials.
For a 10mg retatrutide vial: add 2ml of bacteriostatic water → concentration is exactly 5000 mcg/ml. For a 2mg (2000mcg) starting dose, inject 0.40ml (40 units) on a 100-unit syringe.
Dose Reference Table
Pre-calculated for a 10mg vial + 2ml BAC water = 5,000 mcg/ml concentration. Using a 100-unit (1ml) insulin syringe.
| Dose | Inject Volume (ml) | Syringe Units |
|---|---|---|
| 1000mcg (1mg) | 0.200 ml | 20 units |
| 2000mcg (2mg) | 0.400 ml | 40 units |
| 2500mcg (2.5mg) | 0.500 ml | 50 units |
| 3000mcg (3mg) | 0.600 ml | 60 units |
| 4000mcg (4mg) | 0.800 ml | 80 units |
| 5000mcg (5mg) | 1.000 ml | 100 units |
About Retatrutide
Retatrutide (also called "reta") is a next-generation triple agonist peptide under clinical investigation. It targets three key receptors: GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and glucagon receptors. This triple mechanism is theorized to provide superior metabolic effects compared to dual or single agonists.
For research purposes, retatrutide is typically reconstituted from a lyophilized powder. The most common vial sizes are 5mg, 10mg, and 20mg. When using 2ml of bacteriostatic water per 10mg vial, the resulting concentration is 5,000 mcg/ml — making dosing calculations straightforward.
The half-life of retatrutide is approximately 6 days, which supports once-weekly administration in research protocols. Sources: Jastreboff et al., NEJM 2023 (phase 2 retatrutide trial). Retatrutide is not FDA-approved; human evidence remains limited to early-phase trials. Always consult a qualified healthcare professional before using any research peptide.
How this calculator works
Every result comes from the same three formulas used for any lyophilized peptide: concentration (mcg/ml) = vial mg × 1,000 ÷ BAC water ml; injection volume (ml) = desired dose mcg ÷ concentration; syringe units = injection volume ml × 100 on a U-100 syringe.
For the preset Retatrutide setup on this page: a 10mg vial mixed with 2ml of bacteriostatic water gives a concentration of 5,000 mcg/ml. A 2,000mcg dose then needs 0.40ml, which is 40 units on a 100-unit insulin syringe.
The full methodology, with worked examples and the assumptions behind each formula, is on the methodology page.
Accuracy & limitations
The arithmetic itself is exact — the same inputs always produce the same output. Real-world accuracy depends on things outside the calculator: actual vial contents can vary slightly from the labeled amount within manufacturing tolerance, the BAC water volume should be measured carefully, and syringe readings are taken at the bottom edge of the plunger. Reconstituted peptides also degrade over time (the common guidance is to use within about 28 days refrigerated), which the math does not model. This tool does arithmetic only — it does not recommend doses, and it is not medical advice.
Last reviewed: September 2026 · Content, formulas and sources checked by Kanika
Frequently Asked Questions
How to Use This Retatrutide Calculator
This calculator needs three inputs to produce your injection volume and syringe reading:
- Vial size (mg) — the total retatrutide in your vial. Common sizes are 5mg, 10mg, and 20mg. Check your vial label; do not enter this in mcg.
- BAC water added (ml) — how much bacteriostatic water you injected into the vial during reconstitution. Adding 2ml to a 10mg vial yields 5,000 mcg/ml. Using 4ml gives 2,500 mcg/ml. The calculator updates instantly as you change this value.
- Desired dose (mcg) — how many micrograms you want per injection. Retatrutide is typically dosed in milligrams in clinical literature — convert to mcg by multiplying by 1,000 (e.g. 2mg = 2,000mcg).
The calculator outputs your concentration (mcg/ml), injection volume (ml), and syringe units — the number to draw on a 100-unit (U-100) insulin syringe, where each unit equals 0.01ml. Aim for a result between 10 and 80 units for the most accurate measurement.
If your syringe units fall below 5, consider adding more BAC water to lower the concentration and increase injection volume to a more measurable range. If units exceed 80, use less BAC water or split the dose across two injection sites.
Retatrutide Reconstitution Reference — 2ml BAC Water
All figures below use 2ml of bacteriostatic water. Concentrations and syringe units are calculated automatically for the most common weekly research doses.
| Vial Size | BAC Water | Concentration | 1mg dose | 2mg dose | 4mg dose | 8mg dose |
|---|---|---|---|---|---|---|
| 5mg | 2ml | 2,500 mcg/ml | 0.40ml / 40 units | 0.80ml / 80 units | — | — |
| 10mg | 2ml | 5,000 mcg/ml | 0.20ml / 20 units | 0.40ml / 40 units | 0.80ml / 80 units | — |
| 20mg | 2ml | 10,000 mcg/ml | 0.10ml / 10 units | 0.20ml / 20 units | 0.40ml / 40 units | 0.80ml / 80 units |
Doses above 4mg may require a larger syringe or split across two injections. Use the calculator above for any custom vial size or BAC water volume.