DoseRoutine

Retatrutide Dosage Calculator

Retatrutide ships as a lyophilised powder, so every dose depends on how much bacteriostatic water you added. Enter your vial size, your BAC water volume and the dose you want, and this calculator returns the exact number of units to draw on a U-100 insulin syringe.

This is a unit converter. It converts an amount you already have into volume and syringe units. It does not tell you what to take, and it is educational only — not medical advice. Confirm every amount with your clinician and your product label.

Common setups

Vial size (mg)

Total compound in the vial.

BAC water added (mL)

Volume of bacteriostatic water you reconstitute with.

Target dose

Per-injection dose you want to draw.

Syringe type

U-100 = 100 units per mL (standard). U-40 = 40 units per mL.

Draw

40.0 units

on a U-100 insulin syringe (0.400 mL)

Concentration

5.00 mg/mL

Per dose

2.00 mg

Doses / vial

~5

Retatrutide concentration reference (mg/mL)

What each vial size becomes at common bacteriostatic water volumes.

Vial	+ 1 mL	+ 2 mL	+ 3 mL	+ 5 mL
5 mg	5.00 mg/mL	2.50 mg/mL	1.67 mg/mL	1.00 mg/mL
10 mg	10.00 mg/mL	5.00 mg/mL	3.33 mg/mL	2.00 mg/mL
15 mg	15.00 mg/mL	7.50 mg/mL	5.00 mg/mL	3.00 mg/mL
20 mg	20.00 mg/mL	10.00 mg/mL	6.67 mg/mL	4.00 mg/mL
24 mg	24.00 mg/mL	12.00 mg/mL	8.00 mg/mL	4.80 mg/mL

Retatrutide dosing at a glance

Phase	Dose	Frequency	Notes
Weeks 1–4	1 mg	Once weekly	Trial starting dose in every Phase 2 arm.
Weeks 5–8	2–4 mg	Once weekly	First escalation step; nausea peaks here.
Weeks 9–16	4–8 mg	Once weekly	Escalate only if side effects are tolerable.
Week 16+	8–12 mg	Once weekly	Highest trial arms; 12 mg gave the largest weight loss.

Reference ranges reported in the literature and in common practice — not a prescription, and not personalised advice.

What trips people up

Retatrutide is investigational — it is not FDA-approved and no licensed product exists. Dosing figures come from the Phase 2 trial, not a label.
At 10 mg vial + 2 mL BAC water you get 5 mg/mL, so 1 mg = 20 units on a U-100 syringe. Easy mental maths.
Adding more BAC water does not change the total drug — it only makes each unit smaller and easier to measure accurately.
Under ~10 units per dose, small measuring errors become large percentage errors. Dilute further if your draw is tiny.

How the maths works

Concentration (mg/mL) = vial mg ÷ bacteriostatic water mL.
Volume per dose (mL) = dose mg ÷ concentration.
Syringe units = volume × 100 on a U-100 syringe, or × 40 on a U-40 syringe.
Doses per vial = vial mg ÷ dose mg. Water volume never changes this number.

Retatrutide calculator FAQ

How much BAC water for a 10 mg retatrutide vial?

2 mL is the most common choice: it gives 5 mg/mL, so a 1 mg dose is 20 units, 2 mg is 40 units and 4 mg is 80 units on a U-100 syringe. Use 1 mL if you want a more concentrated vial and smaller draws, or 3 mL if your doses are very small and you want more precision.

How many units of retatrutide is 2 mg?

It depends entirely on concentration. At 5 mg/mL (10 mg vial + 2 mL), 2 mg = 0.4 mL = 40 units on a U-100 syringe. At 10 mg/mL (10 mg + 1 mL), the same 2 mg is only 20 units.

How long does a reconstituted retatrutide vial last?

Refrigerated at 2–8 °C and handled sterilely, most users treat a reconstituted vial as good for about 28–30 days. Bacteriostatic water contains benzyl alcohol, which is what allows multi-dose use; sterile water does not and should be treated as single-use.

Can I skip titration and start at a high dose?

No. The Phase 2 trial escalated every four weeks specifically because gastrointestinal side effects are dose-dependent. Starting high dramatically raises the odds of severe nausea and vomiting.

Retatrutide reference page Check interactions Full retatrutide dosage guide

Educational tool only — not medical advice. Verify every dose with your prescriber and follow sterile technique. See our medical disclaimer.

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