Worked example
Add 2 mL of water to a vial holding 5 mg of Semaglutide. The concentration is 5 ÷ 2 = 2.5 mg/mL, or 2,500 mcg in every millilitre. On a U-100 syringe, where 100 units make 1 mL, each unit holds 25 mcg and each 10 units hold 250 mcg.
Change the water and only the concentration changes. With 4 mL instead, each 10 units hold 125 mcg, half as much, and any given mass takes twice the units to measure. These numbers illustrate the arithmetic; they are not amounts to use.
Concentration table
Common Semaglutide vial sizes against common water volumes. The last column is what 10 units on a U-100 syringe hold.
| Vial | Water | Concentration | 10 units (U-100) hold |
|---|---|---|---|
| 2 mg | 1 mL | 2 mg/mL | 200 mcg |
| 2 mg | 2 mL | 1 mg/mL | 100 mcg |
| 2 mg | 3 mL | 0.667 mg/mL | 66.7 mcg |
| 3 mg | 1 mL | 3 mg/mL | 300 mcg |
| 3 mg | 2 mL | 1.5 mg/mL | 150 mcg |
| 3 mg | 3 mL | 1 mg/mL | 100 mcg |
| 5 mg | 1 mL | 5 mg/mL | 500 mcg |
| 5 mg | 2 mL | 2.5 mg/mL | 250 mcg |
| 5 mg | 3 mL | 1.667 mg/mL | 166.7 mcg |
| 10 mg | 1 mL | 10 mg/mL | 1 mg |
| 10 mg | 2 mL | 5 mg/mL | 500 mcg |
| 10 mg | 3 mL | 3.333 mg/mL | 333.3 mcg |
Notes for Semaglutide vial math
- Because semaglutide vials are small, the result often lands below 10 units. On a 1 mL U-100 syringe the printed marks are every 2 units, so a 0.3 mL or 0.5 mL syringe (marked every unit) gives a finer reading. The calculator warns when a result falls between marks.
- Semaglutide amounts are often written in mg with two decimal places. Typing 0.25 in mg mode and 250 in mcg mode is the same mass; the calculator handles both.
- Many compounded and research products use semaglutide sodium or acetate salts. FDA has said these salts are not the active ingredient in approved semaglutide. A salt also adds mass, so a "5 mg" vial of a salt contains slightly less semaglutide base than 5 mg.
Storage and handling
- For the approved Ozempic pen, the prescribing information allows 56 days after first use, refrigerated or at room temperature up to 30 °C. That applies to Novo Nordisk's preserved formulation only.
- No validated in-use stability data exists for reconstituted research semaglutide. Keep it refrigerated, out of light, unfrozen, and labeled.