Retatrutide Reconstitution Calculator

Mixing Retatrutide: What to Know Before You Reconstitute

1. 01

   Bacteriostatic water vs. sterile water

   Bacteriostatic water is sterile water with 0.9% benzyl alcohol added, a preservative that inhibits bacterial growth once the vial has been punctured. Sterile water carries no preservative and is generally treated as single use. Because a retatrutide vial is drawn from weekly across several weeks, bacteriostatic water is the standard choice. The long service life is precisely why the preservative matters here.

2. 02

   How much water to add

   Water volume sets the concentration, not the amount of peptide. A 10 mg vial contains 10 mg whether you add 1 mL or 3 mL. What changes is how many units you draw for a given dose, and with weekly milligram dosing the practical goal is usually a concentration where a full range of doses stays readable on the syringe.

   Vial	Water	Concentration	Per unit	2 mg draw	4 mg draw
   5 mg	1 mL	5.0 mg/mL	50 mcg	40 units	80 units
   10 mg	1 mL	10.0 mg/mL	100 mcg	20 units	40 units
   10 mg	2 mL	5.0 mg/mL	50 mcg	40 units	80 units
   15 mg	1.5 mL	10.0 mg/mL	100 mcg	20 units	40 units

   A concentration of 10 mg/mL, visible in two rows above, is convenient because every 1 mg is exactly 10 units, which keeps the arithmetic simple across a changing dose. The rows at 5 mg/mL double every draw, which is fine at lower doses but can exceed a 100 unit syringe as doses increase. That is the specific thing to check before committing to a water volume: not just whether today's dose fits, but whether the doses later in the vial will.

3. 03

   Mixing technique

   Run the water down the inside wall of the vial rather than directly onto the powder, then swirl slowly or let it sit until fully dissolved. Do not shake. The solution should be clear with no visible particles. As with any peptide, a vial that stays cloudy after gentle swirling is one most people will not use.

4. 04

   Storage before and after mixing

   Unopened lyophilized vials keep cool and dark. After reconstitution the vial is refrigerated, and the widely followed convention is to discard after about 28 days, a window that comes from punctured bacteriostatic water rather than from the compound. Weekly dosing puts this directly in tension with vial size: a vial holding more than four weeks of doses will reach its discard date with solution still in it. Working out how many doses a vial actually delivers inside that window, before mixing rather than after, is the practical planning step. The doses per vial figure in the calculator above and the expiration countdown in PepKit are two ways to keep that visible.

5. 05

   The syringe

   U-100 insulin syringes, where 100 units equal 1 mL and each unit is 0.01 mL. Milligram doses produce large draws, so the 1 mL 100 unit syringe is the usual choice. At lower concentrations, higher doses can approach or exceed a full syringe, which is the situation a more concentrated mix avoids.

6. 06

   Common mistakes worth avoiding

   The recurring ones: choosing a water volume that works for a starting dose but not for a later one, carrying a unit count over from the previous vial without rechecking it against the new mix, letting a large vial run past its discard date because solution remains, confusing mg and mcg during conversion, and doing the math from memory each week rather than working it out once when the vial is mixed.