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How-to · reconstitution
Put 2 mL of bacteriostatic water into the 10 mg Semaglutide vial. That makes 5.00 mg/mL. A 0.25 mg dose is then 5.0 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 Semaglutide in the glass never changes. Only the number of marks it takes does.
Semaglutide is the drug in Wegovy, Ozempic and Rybelsus. It copies a gut hormone called GLP-1, which helps control appetite and blood sugar.
| Water added | Concentration | Per U-100 unit | Example: 0.25 mg = |
|---|---|---|---|
| 1 mL | 10.00 mg/mL | 100 mcg | 2.5 units |
| 2 mL | 5.00 mg/mL | 50 mcg | 5.0 units |
Straight arithmetic: concentration = 10 mg ÷ water, and 1 U-100 unit = 0.01 mL. The example column shows the math at 0.25 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.
0.25 mg once weekly for 4 weeks, under the skin.
| Water added | Concentration | Draw |
|---|---|---|
| 1 mL | 10.00 mg/mL | 2.5 units |
| 2 mL | 5.00 mg/mL | 5.0 units |
FDA labelWegovy (semaglutide) — FDA-approved Prescribing Information (DailyMed) · retrieved 2026-08-20
1.7–2.4 mg once weekly, under the skin.
| Water added | Concentration | Draw, low to high |
|---|---|---|
| 1 mL | 10.00 mg/mL | 17.0 to 24.0 units |
| 2 mL | 5.00 mg/mL | 34.0 to 48.0 units |
FDA labelWegovy (semaglutide) — FDA-approved Prescribing Information (DailyMed) · retrieved 2026-08-20
At the worked amount, the vial contains forty doses while the stated storage window covers four. This is the largest mismatch among the documented semaglutide vials.
At the schedule’s opening amount this vial holds most of a year and the mixed solution keeps for a month. The gap is not marginal; it is the whole purchase.
Buying a larger vial to lower the cost per milligram raises the cost per usable dose here. The mixing table gives no sign of that.
Mixed into the least water, an opening dose covers between two and three units, and there is no graduation at two and a half. The larger listed volume doubles the reading and lands it on a mark.
On the biggest vial in the family the draw is the hardest to read. That is the opposite of what most people expect from more powder.
Read against the top of the labeled schedule, this vial holds four doses and empties exactly as the window shuts.
So there is a pairing where this size is the right one. It is simply not the pairing anyone is in during their first month.
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 Semaglutide calculator →The arithmetic on this page is only half the question. These are the pages that carry the other half.