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How-to · reconstitution
Put 1 mL of bacteriostatic water into the 20 mg Retatrutide vial. That makes 20.00 mg/mL. A 2 mg dose is then 10.0 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 | 20.00 mg/mL | 200 mcg | 10.0 units |
| 2 mL | 10.00 mg/mL | 100 mcg | 20.0 units |
Straight arithmetic: concentration = 20 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 20 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 | 20.00 mg/mL | 5.0 to 60.0 units |
| 2 mL | 10.00 mg/mL | 10.0 to 120.0 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
Twice the powder of the small vial and twice the doses, with both listed volumes still landing on syringe lines. It also produces a reading that already exists one page down the ladder.
Concentration is vial divided by water, so doubling both leaves it unchanged. Mixed into the larger listed volume, this vial gives precisely the strength and precisely the draw that the smallest vial gives at the smaller volume.
That is worth naming because it is the trap. A unit count copied between the two pages happens to be right, which teaches exactly the wrong lesson. It confirms nothing about which vial is in your hand.
The vial divides into ten worked amounts, but no published source says how long the mixed solution keeps. Ten doses does not establish ten weeks of use.
For an investigational compound with no approved label, that distinction is the whole of what this page can honestly offer.
Both water options land exactly on syringe lines. With the largest retatrutide vial, neither does because the worked amount no longer divides evenly.
Nothing about the compound changes between the two pages. The legibility of the answer 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.