How much water for a 20 mg Semaglutide vial
The water volume is the one number you choose. It doesn't change how much Semaglutide is in the vial. It changes how many units each milligram takes up. The table compares common volumes for 0.25 mg:
| Water added | mg/mL | mcg per unit | Units for 0.25 mg | Smallest U-100 barrel |
|---|---|---|---|---|
| 0.5 mL | 40 | 400 | 0.6 | 30-unit |
| 1 mL | 20 | 200 | 1.3 | 30-unit |
| 1.5 mL | 13.33 | 133.3 | 1.9 | 30-unit |
| 2 mL | 10 | 100 | 2.5 | 30-unit |
| 2.5 mL | 8 | 80 | 3.1 | 30-unit |
| 3 mL | 6.67 | 66.67 | 3.8 | 30-unit |
| 4 mL | 5 | 50 | 5 | 30-unit |
| 5 mL | 4 | 40 | 6.3 | 30-unit |
Working backwards: to make 0.25 mg read exactly 10 units, add 8 mL; for 20 units, add 16 mL. The BAC water calculator does this for any reading.
Semaglutide 20 mg: mg → units charts
One chart per common water volume. Rows are reference increments, not suggested amounts. Amber values exceed a 100-unit (1 mL) barrel.
20 mg + 1 mL (20 mg/mL)
| Amount | mcg | Volume (mL) | Syringe units |
|---|---|---|---|
| 0.1 mg | 100 | 0.005 | 0.5 |
| 0.25 mg | 250 | 0.013 | 1.3 |
| 0.5 mg | 500 | 0.025 | 2.5 |
| 0.75 mg | 750 | 0.038 | 3.8 |
| 1 mg | 1,000 | 0.05 | 5 |
| 1.5 mg | 1,500 | 0.075 | 7.5 |
| 1.7 mg | 1,700 | 0.085 | 8.5 |
| 2 mg | 2,000 | 0.1 | 10 |
| 2.4 mg | 2,400 | 0.12 | 12 |
| 3 mg | 3,000 | 0.15 | 15 |
| 4 mg | 4,000 | 0.2 | 20 |
| 5 mg | 5,000 | 0.25 | 25 |
20 mg + 2 mL (10 mg/mL)
| Amount | mcg | Volume (mL) | Syringe units |
|---|---|---|---|
| 0.1 mg | 100 | 0.01 | 1 |
| 0.25 mg | 250 | 0.025 | 2.5 |
| 0.5 mg | 500 | 0.05 | 5 |
| 0.75 mg | 750 | 0.075 | 7.5 |
| 1 mg | 1,000 | 0.1 | 10 |
| 1.5 mg | 1,500 | 0.15 | 15 |
| 1.7 mg | 1,700 | 0.17 | 17 |
| 2 mg | 2,000 | 0.2 | 20 |
| 2.4 mg | 2,400 | 0.24 | 24 |
| 3 mg | 3,000 | 0.3 | 30 |
| 4 mg | 4,000 | 0.4 | 40 |
| 5 mg | 5,000 | 0.5 | 50 |
20 mg + 3 mL (6.67 mg/mL)
| Amount | mcg | Volume (mL) | Syringe units |
|---|---|---|---|
| 0.1 mg | 100 | 0.015 | 1.5 |
| 0.25 mg | 250 | 0.038 | 3.8 |
| 0.5 mg | 500 | 0.075 | 7.5 |
| 0.75 mg | 750 | 0.112 | 11.2 |
| 1 mg | 1,000 | 0.15 | 15 |
| 1.5 mg | 1,500 | 0.225 | 22.5 |
| 1.7 mg | 1,700 | 0.255 | 25.5 |
| 2 mg | 2,000 | 0.3 | 30 |
| 2.4 mg | 2,400 | 0.36 | 36 |
| 3 mg | 3,000 | 0.45 | 45 |
| 4 mg | 4,000 | 0.6 | 60 |
| 5 mg | 5,000 | 0.75 | 75 |
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How much one draw can hold
A barrel's capacity caps the largest amount you can measure in one draw. The cap depends on concentration:
| Water | 30 units (0.3 mL) | 50 units (0.5 mL) | 100 units (1 mL) |
|---|---|---|---|
| 1 mL | 6 mg | 10 mg | 20 mg |
| 1.5 mL | 4 mg | 6.67 mg | 13.33 mg |
| 2 mL | 3 mg | 5 mg | 10 mg |
| 2.5 mL | 2.4 mg | 4 mg | 8 mg |
| 3 mL | 2 mg | 3.33 mg | 6.67 mg |
Draws per 20 mg vial
Whole draws of each reference amount the vial contains, regardless of water volume (the water changes the reading, not the total):
| Amount per draw | Whole draws | Left over |
|---|---|---|
| 0.1 mg | 200 | 0 mg |
| 0.25 mg | 80 | 0 mg |
| 0.5 mg | 40 | 0 mg |
| 0.75 mg | 26 | 0.5 mg |
| 1 mg | 20 | 0 mg |
| 1.5 mg | 13 | 0.5 mg |
| 1.7 mg | 11 | 1.3 mg |
| 2 mg | 10 | 0 mg |
| 2.4 mg | 8 | 0.8 mg |
| 3 mg | 6 | 2 mg |
| 4 mg | 5 | 0 mg |
| 5 mg | 4 | 0 mg |
Real-world yield is usually lower: some liquid stays in the vial and in the syringe's dead space.
Other Semaglutide vial sizes
Or go back to the main Semaglutide calculator, which compares every size side by side.
Frequently asked questions
How much bacteriostatic water do I add to a 20 mg Semaglutide vial?
Any volume works mathematically; the choice sets the concentration. 1 mL gives 20 mg/mL (200 mcg per U-100 unit); 2 mL gives 10 mg/mL (100 mcg per U-100 unit); 3 mL gives 6.67 mg/mL (66.67 mcg per U-100 unit). 2 mL is a common choice because it keeps the arithmetic round.
How many units is 0.25 mg from a 20 mg Semaglutide vial?
With 1 mL: 1.3 units. With 2 mL: 2.5 units. With 3 mL: 3.8 units. The amount of Semaglutide is the same in every case; only the volume it is dissolved in changes.
How many mg of Semaglutide is 10 units from a 20 mg vial?
10 units on a U-100 syringe is 0.1 mL. With 1 mL of water that is 2 mg; With 2 mL of water that is 1 mg; With 3 mL of water that is 0.667 mg.
How much Semaglutide fits in one syringe from a 20 mg vial?
At 10 mg/mL (2 mL of water), a 30-unit barrel holds up to 3 mg, a 50-unit barrel 5 mg and a 100-unit barrel 10 mg per draw.
Is this a dosing chart?
No. These are arithmetic tables for converting an amount into a syringe reading for a given vial. They do not recommend any amount or schedule.
Storing the Semaglutide vial after mixing
Reconstitution changes how a vial has to be kept: a lyophilized powder and a solution have different temperature, light and time limits, and an opened multi-dose diluent vial has its own clock (CDC guidance: discard 28 days after first puncture unless the manufacturer gives another date). The peptide storage guide covers both states, and the bacteriostatic water guide covers the diluent. Label each vial with the amount, the water added, the concentration and the date.
Sources
- Wegovy (semaglutide) injection: full prescribing information (revised 06/2026)
- FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products
- FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products
Links checked 2026-10-19.