how much bacteriostatic water to add
For 250 mcg to read 10 units from a 5 mg vial, add 2 mL of bacteriostatic water (2.5 mg/mL).
Pick the reading you want on the syringe and the calculator gives the bacteriostatic water to add. The chart below shows what common volumes give for each vial size.
syringe · picked to fit the draw
price, vial size and certificate correction
USD
mL
Most 2–15 mg vials hold 3 mL.
add 2 mL
of bacteriostatic water · 2.5 mg/mL
the working
- 5 mg × 10 ÷ (250 mcg × 100) = 2 mL of water
If this is a prescription, the dose and volume on your pharmacy label take priority. Ask your pharmacist about any mismatch.
bacteriostatic water chart
what each volume gives
| vial | 0.5 mL | 1 mL | 1.5 mL | 2 mL | 2.5 mL | 3 mL |
|---|---|---|---|---|---|---|
| 2 mg | 4 mg/mL 250 mcg = 6.25 u | 2 mg/mL 250 mcg = 12.5 u | 1.333 mg/mL 250 mcg = 18.75 u | 1 mg/mL 250 mcg = 25 u | 0.8 mg/mL 250 mcg = 31.25 u | 0.667 mg/mL 250 mcg = 37.5 u |
| 5 mg | 10 mg/mL 250 mcg = 2.5 u | 5 mg/mL 250 mcg = 5 u | 3.333 mg/mL 250 mcg = 7.5 u | 2.5 mg/mL 250 mcg = 10 u | 2 mg/mL 250 mcg = 12.5 u | 1.667 mg/mL 250 mcg = 15 u |
| 10 mg | 20 mg/mL 250 mcg = 1.25 u | 10 mg/mL 250 mcg = 2.5 u | 6.667 mg/mL 250 mcg = 3.75 u | 5 mg/mL 250 mcg = 5 u | 4 mg/mL 250 mcg = 6.25 u | 3.333 mg/mL 250 mcg = 7.5 u |
| 15 mg | 30 mg/mL 250 mcg = 0.83 u | 15 mg/mL 250 mcg = 1.67 u | 10 mg/mL 250 mcg = 2.5 u | 7.5 mg/mL 250 mcg = 3.33 u | 6 mg/mL 250 mcg = 4.17 u | 5 mg/mL 250 mcg = 5 u |
| 20 mg | 40 mg/mL 250 mcg = 0.63 u | 20 mg/mL 250 mcg = 1.25 u | 13.333 mg/mL 250 mcg = 1.88 u | 10 mg/mL 250 mcg = 2.5 u | 8 mg/mL 250 mcg = 3.13 u | 6.667 mg/mL 250 mcg = 3.75 u |
| 30 mg | 60 mg/mL 250 mcg = 0.42 u | 30 mg/mL 250 mcg = 0.83 u | 20 mg/mL 250 mcg = 1.25 u | 15 mg/mL 250 mcg = 1.67 u | 12 mg/mL 250 mcg = 2.08 u | 10 mg/mL 250 mcg = 2.5 u |
u = units on a U-100 syringe. Readings under 2 units are hard to measure; above 100 units needs more than one 1 mL syringe.
five steps
how to reconstitute a vial
- Note the amount in the vial (mg or IU) from the label, or the measured content from the lot certificate.
- Choose the bacteriostatic water volume. More water lowers the concentration, so each draw reads more units.
- Add the water slowly down the inside wall of the vial and swirl gently until it dissolves; do not shake.
- Divide the vial amount by the water for the concentration, then the amount per draw by the concentration for mL. Multiply by 100 for U-100 units.
- Read the draw on the nearest printed mark of your syringe, and write the mix date on the vial.
what the numbers mean · where they come from
terms and sources
- Label amount or measured amount. The calculator starts from the amount printed on the vial. A lot certificate’s measured content (net peptide content, in mg) can replace it for the vial that was tested. HPLC purity is a share of peak area, not a mass, so a purity-only correction is shown as an estimate. See HPLC, certificate of analysis and how to read a peptide COA.
- Concentration. Amount in the vial ÷ water added. Terms: reconstitution, bacteriostatic water, lyophilized.
- Syringe units. A volume: 0.01 mL per unit on a U-100 syringe, 0.025 mL on U-40. Units say nothing about the compound until the concentration is known.
- Cost per draw. Vial price × amount per draw ÷ vial amount, from the price per mg of a current offer. Price history: peptide price tracker.
Arithmetic only, on the numbers entered. Amounts from labels or trials are cited references, not recommendations; PeptideTech does not give personal use instructions and does not test products.
short answers
calculator questions
How much BAC water do I add to a 5 mg vial?
2 mL is common: it gives 2.5 mg/mL, so 250 mcg is 10 units on a U-100 syringe. 1 mL gives 5 mg/mL (250 mcg = 5 units) and 2.5 mL gives 2 mg/mL (250 mcg = 12.5 units). The right amount is the one whose draws land on your syringe marks.
How much BAC water do I add to a 10 mg vial?
2 mL gives 5 mg/mL (250 mcg = 5 units, 1 mg = 20 units); 3 mL gives 3.33 mg/mL (250 mcg = 7.5 units). If the vial holds more, 4 mL puts 250 mcg exactly on 10 units.
Can I add too much bacteriostatic water?
Only beyond what the vial holds (usually 3 mL for 2–10 mg vials) or when each draw becomes too large for your syringe. More water never changes the amount of compound in the vial, only the units per draw.
Sterile water or bacteriostatic water?
Bacteriostatic water contains 0.9% benzyl alcohol, which inhibits bacterial growth in a vial that is punctured more than once; sterile water does not. The arithmetic is the same for either.
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