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Wegovy calculator (semaglutide)
Wegovy ships as a pen, but compounded/vialed semaglutide needs reconstituting. Enter your vial mg, the bac water you added, and your dose for the exact units, mL, and doses per vial.
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.
Wegovy vs Ozempic: same molecule, different product
Wegovy and Ozempic are both semaglutide, so the reconstitution arithmetic above is identical for either. The products are not identical. These are the handling rules each one's own FDA label sets — the differences that a shared molecule name hides.
| Product | Presentation | Before use | Once in use |
|---|---|---|---|
| Wegovy | single-dose pen | 2–8 °C | 28 days · 8–30 °C Applies before the pen cap is removed. |
| 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 |
So the molecule is the same and the handling is not. Getting this wrong is the most common storage mistake with semaglutide: a rule read off the wrong brand's carton. Follow the carton in your own hand — more detail on the storage page.
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.
How long can Wegovy stay out of the fridge?
Per its own FDA label, once in use — single-dose pen: 28 days, 8–30 °C. Unopened it stays at 2–8 °C. Always follow the carton you actually have; this is a restatement of the label, not advice.
Is Wegovy the same as Ozempic?
Both are semaglutide, so the reconstitution arithmetic on this page is identical for either. The handling is not identical — the in-use windows above come from each product's own label and they differ.
Where is Wegovy available?
Wegovy is marketed in all five markets we track — US, UK, Germany, Japan, Australia — per each country's regulator register.
Other calculators
Keep reading
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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