⚡ Retatrutide Dosage Calculator
Pick your syringe, enter vial quantity, bacteriostatic water volume, and desired dose — concentration, draw volume, and doses per vial computed instantly.
Retatrutide Reconstitution & Dosing
Retatrutide (LY3437943) is a novel triple receptor agonist targeting GLP-1, GIP, and glucagon receptors simultaneously — producing superior weight reduction outcomes compared to dual-agonist compounds in Phase 3 trials. Like semaglutide and tirzepatide, retatrutide is sold as a lyophilised powder that must be reconstituted with bacteriostatic water before subcutaneous injection. The reconstitution volume you choose determines your solution concentration and directly controls how many syringe units to draw for every dose.
This calculator handles the maths in real time. Select your syringe size, vial quantity, BAC water volume, and target dose — results update immediately with the exact draw instructions. A visual draw guide shows your position on the syringe scale.
You have a 10 mg retatrutide vial, add 1 mL BAC water, and want a 2 mg (2,000 mcg) weekly dose on a 0.3 mL U-100 syringe.
- Concentration = (10 × 1,000) ÷ 1 = 10,000 mcg/mL
- Volume = 2,000 ÷ 10,000 = 0.2 mL
- U-100 draw = 0.2 × 100 = pull to the 20-unit mark
- Doses per vial = floor(10,000 ÷ 2,000) = 5 doses
What is the total volume of your syringe?
Select Retatrutide vial quantity
How much bacteriostatic water?
How much Retatrutide do you want in each dose?
Select your inputs above to generate your draw guide.
Based on LY3437943 TRIUMPH trial protocol — 1 subcutaneous injection per week. Phases are 4 weeks each. Individual tolerance may vary; this is a research reference only.
| Phase | Weeks | Weekly Dose | Doses / Phase | 10 mg Vials | 20 mg Vials | Draw (1 mL BAC / 10 mg vial) |
|---|---|---|---|---|---|---|
| Phase 1 — Intro | 1–4 | 1 mg (1,000 mcg) | 4 | 1 | 1 | 10 units U-100 |
| Phase 2 | 5–8 | 2 mg (2,000 mcg) | 4 | 1 | 1 | 20 units U-100 |
| Phase 3 | 9–12 | 4 mg (4,000 mcg) | 4 | 2 | 1 | 40 units U-100 |
| Phase 4 | 13–16 | 8 mg (8,000 mcg) | 4 | 4 | 2 | 80 units U-100 |
| Phase 5 — Maintenance | 17+ | 12 mg (12,000 mcg) | 4+ | 6+ | 3+ | 120 units U-100 (1.2 mL) * |
* Phase 5 at 12 mg requires 1.2 mL per injection with 1 mL BAC water — use a 1.0 mL syringe in two separate injections (0.6 mL each site), or reconstitute with 0.5 mL BAC water for a 60-unit draw on a 0.5 mL syringe (24,000 mcg/mL concentration). Use the calculator above to find the combination that works for your vial and syringe.
Retatrutide Calculator — Frequently Asked Questions
What is retatrutide and how does it differ from semaglutide?
Retatrutide (LY3437943) is a triple receptor agonist targeting GLP-1, GIP (glucose-dependent insulinotropic polypeptide), and glucagon receptors simultaneously. Semaglutide is a single GLP-1 agonist. The additional GIP and glucagon receptor activity in retatrutide produces greater energy expenditure, more pronounced lipolysis, and superior weight reduction in Phase 3 trials. The TRIUMPH-1 trial demonstrated average weight loss of approximately 24% of body weight over 48 weeks at the 12 mg dose — compared to ~15–17% for semaglutide 2.4 mg at 68 weeks.
How much BAC water should I add to a retatrutide vial?
The ideal BAC water volume depends on your dose and syringe capacity. For a comfortable 0.2 mL (20 units on U-100) draw: use the concentration formula to work backwards from your target draw volume. For a 2 mg (2,000 mcg) dose on a standard 10 mg vial: adding 1 mL gives 10,000 mcg/mL, yielding exactly 0.2 mL (20 units). For higher doses such as 8 mg per week, 1 mL BAC water gives 0.8 mL (80 units) — still within a 1.0 mL syringe. Adjust BAC water to keep the draw volume within your syringe's capacity.
Why does the high-dose phase require a larger syringe?
At maintenance doses of 12 mg per week, a 10 mg vial reconstituted with 1 mL BAC water produces 10,000 mcg/mL. The required volume = 12,000 ÷ 10,000 = 1.2 mL — which exceeds standard 0.3 mL and 0.5 mL syringe capacity and even a 1.0 mL syringe. Solutions: (1) use a 20 mg or 30 mg vial to reduce the number of vials used; (2) reconstitute with less BAC water (e.g. 0.5 mL) to increase concentration so the volume fits a smaller syringe; or (3) split the 1.2 mL dose across two separate injection sites using two 0.6 mL draws.
How long does a reconstituted retatrutide vial remain stable?
Once reconstituted with bacteriostatic water and stored refrigerated at 2–8°C, retatrutide should be used within 28 days — the standard window for BAC water preserved peptides. Label each vial with the reconstitution date immediately. Do not freeze the reconstituted solution. Weekly injections from a single 10 mg vial during Phase 1 (4 doses of 1 mg) fit comfortably within this window.
What syringe size is best for retatrutide injections?
During Phase 1–2 (1–2 mg doses), a 0.3 mL or 0.5 mL U-100 insulin syringe (29–31G, 0.5" needle) is ideal. As the titration progresses to Phase 3 (4 mg) and beyond, switch to a 1.0 mL U-100 syringe. All doses must be calculated using U-100 (100 units/mL) unit counting — never U-40. Use the calculator above to determine the exact draw for each phase.
Is retatrutide approved by the FDA?
As of 2026, retatrutide (LY3437943) is under active clinical development by Eli Lilly. It has completed Phase 3 trials with strong efficacy data but has not received FDA approval for commercial use. It is available for research purposes only and should be used strictly within that context. All decisions regarding its use remain the sole responsibility of qualified researchers and should comply with applicable regulations in your jurisdiction.