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How-to · reconstitution
Put 1 mL of bacteriostatic water into the 10 mg Retatrutide vial. That makes 10.00 mg/mL. A 2 mg dose is then 20.0 units on a U-100 syringe.
That volume is the one that lands the draw on a syringe line, so the reading can be checked by eye. More water makes a weaker mix and a bigger draw. Less water makes a stronger mix and a smaller one. The amount of Retatrutide in the glass never changes. Only the number of marks it takes does.
Retatrutide is an experimental weekly injection being tested for weight loss. It acts on three hormone signals linked to appetite and metabolism.
| Water added | Concentration | Per U-100 unit | Example: 2 mg = |
|---|---|---|---|
| 1 mL | 10.00 mg/mL | 100 mcg | 20.0 units |
| 2 mL | 5.00 mg/mL | 50 mcg | 40.0 units |
Straight arithmetic: concentration = 10 mg ÷ water, and 1 U-100 unit = 0.01 mL. The example column shows the math at 2 mg; it is not a dose recommendation.
Which volume to use is a practical choice rather than a dose. Pick the one that puts your draw somewhere you can actually read it on the syringe. The flags in the last column mark where that fails. “Hard to measure” means the draw is too small to judge by eye. “Won’t fit” means it is bigger than one U-100 syringe holds.
The table above uses one worked example. These are the published quantities, converted into marks on a U-100 barrel at each water volume for a 10 mg vial. Where a quantity was never studied by injection, the row says so.
1–12 mg once weekly, under the skin.
| Water added | Concentration | Draw, low to high |
|---|---|---|
| 1 mL | 10.00 mg/mL | 10.0 to 120.0 unitswon’t fit |
| 2 mL | 5.00 mg/mL | 20.0 to 240.0 unitswon’t fit |
Human trialJastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med 2023;389:514-26 (PMID 37366315) · retrieved 2026-08-12
At the worked amount, the vial contains five doses. Both water options land exactly on syringe lines, although the compound has no approved prescribing label.
No cited source says how long a mixed vial keeps, so no storage window is shown. The doses-per-vial count is the only supported supply figure here.
Other compounds have a labeled storage window to compare with the dose count. This one does not, so no storage period is estimated.
Each water option lands the worked dose exactly on a syringe line, so no rounding is needed.
That will not hold across the whole ladder. The largest retatrutide vial breaks it.
A whole-number draw only proves that the arithmetic divided evenly. It does not prove that the vial, water or entered amount was correct.
The trial doses spanned more than tenfold. At the lower amounts, this vial lasts considerably longer than it does in the worked example.
Somebody reading the top arms empties it in a couple of draws. The vial does not change; which end of the range you are reading does.
The table shows the offered water volumes. The calculator does the same arithmetic for any volume and any syringe, and shows its working line by line.
Open the Retatrutide calculator →The arithmetic on this page is only half the question. These are the pages that carry the other half.