Retatrutide Calculator

Retatrutide reconstitution chart

Retatrutide comes as a powder. The vial size is the total milligrams of retatrutide in it, and before the first dose you dissolve it in bacteriostatic (BAC) water. How much water you add sets how much retatrutide is in each unit on the syringe, so the chart is read in three steps: find your vial size in the first column, add the BAC water shown in the second, and read across to your dose. The number in that cell is how many units to draw on a standard 100-unit insulin syringe.

This chart uses one mix for every row, 1 mL of BAC water per 10 mg in the vial, because it makes every 1 mg of retatrutide 10 units. So if you want to know how much BAC water for 10mg retatrutide, that row says 1 mL, and a 4 mg dose from it is 40 units. The per-vial tables further down use the 2 mL mix most people log; both are correct, the units just differ. Tap a row to load that vial and water into the reta calculator above, which works as a retatrutide BAC water calculator for any mix.

Units are marks on a 100-unit (U-100) insulin syringe; 100 is a full 1 mL syringe. The doses across the top are the ones people look up, from 1 mg to 10 mg; none of them is a recommendation. * Above 30 mg the 1 mL-per-10 mg mix would need 4 to 5 mL, more than most vials hold, so 40 mg is shown at 2 mL (1 mg = 5 units) and 50 mg at 3 mL (1 mg = 6 units).

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Dose Calculation: The Math Explained

The formula is the same for any reconstituted peptide:

Worked example. A 12mg vial reconstituted with 2mL of BAC water has a concentration of 12 ÷ 2 = 6 mg/mL. For a 4mg weekly dose: (4 ÷ 6) × 100 = 66.7 units. Round to 67 units. That 12mg vial at 4mg per week gives you 3 weekly doses, roughly 3 weeks per vial.

Common Vial Sizes and Dose Charts

Among Regimen users tracking retatrutide, the most common vial is 10mg (39%), followed by 20mg (23%) and 30mg (16%). Most reconstitute with 2mL of bacteriostatic water (41%), then 1mL (28%) and 3mL (26%). The most commonly logged weekly dose is 2mg.

5mg Vial + 1mL BAC Water (5.0 mg/mL)

10mg Vial: How Much BAC Water?

2mL is the usual answer, and it is the one to use while you are titrating. It gives 5 mg/mL, which puts the early doses in the easiest part of the syringe to read. Use 1mL instead once you are dosing 6mg a week or more: at 5 mg/mL a 5mg dose already fills a 1mL barrel to the 100-unit mark, and anything above that will not fit in one draw.

Either mix holds the same 10mg of retatrutide. More water does not mean more drug, it just spreads the same amount over more volume, so each dose is a bigger number of units.

One thing the doses-per-vial column does not tell you: once mixed, the vial gets about 28 days in the fridge, which is four weekly shots comfortably and a fifth only if you draw it on day 28 itself. At 2mg a week a 10mg vial is a clean fit. At 1mg a week you would need ten weeks to finish it, so half of it gets thrown away. Match the vial to about four weeks of your dose, not to the biggest number of doses on paper.

12mg Vial + 2mL BAC Water (6.0 mg/mL)

20mg Vial + 2mL BAC Water (10.0 mg/mL)

30mg Vial + 3mL BAC Water (10.0 mg/mL)

Titration Schedule

The Phase 2 retatrutide trial used a slow titration: 2mg per week for 4 weeks, then 4mg for 4 weeks, then 8mg for 4 weeks, then 12mg as maintenance. Not everyone reaches 12mg. Many people stabilize at 4 or 8mg per week once appetite and weight loss are where they want them. Hold any tier longer if GI side effects do not settle within a week of dose increase.

Storage After Reconstitution

Give reconstituted retatrutide 28 days in the fridge at 36 to 46°F (2 to 8°C), and treat that as a ceiling rather than a guarantee. Two clocks run at once: the bacteriostatic water’s preservative, which USP caps at 28 days after the vial is first punctured, and retatrutide’s own stability in solution, which nobody has published. The beyond-use date is whichever runs out first, so 28 days is the most you should assume and less is safer. Discard sooner if it turns cloudy or changes colour. Keep the vial upright, away from light, and never freeze it. Discard if the solution becomes cloudy, develops particles, or changes color. Match vial size to your weekly dose so you finish the vial inside that window - large vials at small doses waste compound.

Mixing Steps

1. Swab the tops of both the retatrutide vial and the BAC water vial with alcohol. Let them dry, about 15 to 30 seconds.
2. Draw your chosen volume of BAC water (typically 1 to 3mL, up to 5mL for the largest vials) into an insulin syringe.
3. Insert the needle into the retatrutide vial at an angle and let the water run slowly down the inside glass wall. Do not aim directly at the powder.
4. Gently swirl or roll the vial between your palms. Retatrutide can take up to 8 minutes to fully dissolve. Do not shake.
5. Check the solution. It should be completely clear with no particles or cloudiness before you draw your first dose.

See also: full retatrutide reconstitution guide, retatrutide dosing guide, titration schedule, injection sites, side effects, and switching from tirzepatide.

Educational reference only. Not medical advice. Retatrutide is investigational and not FDA approved. Work with a licensed clinician on dosing and monitoring.