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Semaglutide reconstitution calculator
Mixing compounded or vialed semaglutide? Enter your vial strength, the bacteriostatic water you added, and your target dose — get the exact syringe units, mL, doses per vial, and cost per dose, with guardrails that catch the common mistakes.
GLP-1 (Ozempic/Wegovy molecule; also compounded).
"Units" are a volume marking, not a drug amount — the same units = a different mg every time the vial is mixed differently.
Vial size × bacteriostatic water: what each combination gives you
The same vial gives a different concentration depending on how much water you add. Find your vial size and the water you added; the last column is what one milligram is worth in syringe units.
| Vial | Bac water added | Concentration | 1 mg draws |
|---|---|---|---|
| 2 mg | 1 mL | 2 mg/mL | 50 U |
| 2 mg | 2 mL | 1 mg/mL | 100 U |
| 2 mg | 3 mL | 0.67 mg/mL | 150 U |
| 4 mg | 1 mL | 4 mg/mL | 25 U |
| 4 mg | 2 mL | 2 mg/mL | 50 U |
| 4 mg | 3 mL | 1.33 mg/mL | 75 U |
| 5 mg | 1 mL | 5 mg/mL | 20 U |
| 5 mg | 2 mL | 2.5 mg/mL | 40 U |
| 5 mg | 3 mL | 1.67 mg/mL | 60 U |
| 10 mg | 1 mL | 10 mg/mL | 10 U |
| 10 mg | 2 mL | 5 mg/mL | 20 U |
| 10 mg | 3 mL | 3.33 mg/mL | 30 U |
Units are for a standard U-100 insulin syringe, where 100 units = 1 mL. These are conversions, not dose suggestions — your dose comes from your prescriber, and this page never proposes one. For a size or volume not listed, use the calculator above.
Brands of semaglutide, and how their handling rules differ
There is more than one brand of semaglutide, and the brands do not share handling rules. Each row below is that product's own FDA label.
| Product | Presentation | Before use | Once in use |
|---|---|---|---|
| Ozempic | multi-dose pen | 2–8 °C | 56 days · 15–30 °C |
| Ozempic | single-dose prefilled syringe | 2–8 °C | 28 days · 8–30 °C |
| Wegovy | single-dose pen | 2–8 °C | 28 days · 8–30 °C Applies before the pen cap is removed. |
Dosing is once weekly, and the published half-life of semaglutide is ~168 h.
Label sources: Ozempic FDA label (DailyMed), §16 · Wegovy FDA label (DailyMed), Instructions for Use
FAQ
How many units is my dose?
Units are a volume marking on the syringe, not a drug amount — on a U-100 syringe, 100 units = 1 mL. The units for any dose depend entirely on how the vial was reconstituted (mg of powder ÷ mL of bacteriostatic water). Enter your numbers above and the calculator gives the exact units.
How much bacteriostatic water should I add?
There's no single right amount — more water makes the solution more dilute (easier to draw, larger volume per dose) and less water makes it more concentrated. Pick a volume, enter it above, and the calculator shows the resulting concentration, units per dose, and doses per vial so you can choose a readable draw.
What's a typical semaglutide vial?
Compounded and research semaglutide commonly comes as 2, 4, 5, or 10 mg of dry powder. Use the preset buttons above to prefill, then enter the water volume you actually added.
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Sources
This tool converts the numbers you enter — it never recommends a dose. Its constants are cited below; the warnings are arithmetic checks, not clinical limits.
- Syringe "units" are a volume marking, not a drug amount: a U-100 syringe reads 100 units = 1 mL (U-40 = 40 units/mL). The calculator converts mg ↔ mL ↔ units on this standard — it never assumes units equal mg.Standard insulin concentration, U-100 = 100 units/mL (PMC5505430) ↗
- The volume to draw is (drug ordered ÷ drug available) × the vial's total mL — i.e. dose ÷ concentration, where concentration (mg/mL) = vial mg ÷ bacteriostatic water mL. You enter every number; the tool only does this arithmetic.Dose-volume formula — StatPearls "Dose Calculation" (Bookshelf NBK430836) ↗
- An opened (punctured) multi-dose vial is dated and discarded within 28 days unless the manufacturer states otherwise.CDC Injection Safety (per USP General Chapter <797>) ↗
Educational calculator only — not medical advice and not a recommended dose. You enter your own numbers; we only do the arithmetic. Some products are not approved for human use; verify your product and dose with a licensed clinician.
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