Dosify Me
Dosify Me
Home · Calculator · BAC water
Work backwards from the syringe. Pick the unit mark you want your dose to land on, and this gives the exact volume of bacteriostatic water to add to the vial.
Add this much bacteriostatic water: —
Resulting concentration: —
Draw: —
Keep this calculation in your pocket. Save your vials, schedule and dose log in Dosify Me for Android.
Water volume is a choice, not a fixed rule. Here is what your dose reads as on the syringe at each of the volumes people commonly use — useful when the exact figure above is awkward and a round 2 mL or 3 mL is easier to measure.
| BAC water | Concentration | Per unit | Your dose reads |
|---|
One insulin unit is 0.01 mL, so 100 units is 1 mL. That never changes — a U-50 syringe has the same 0.01 mL per unit as a U-100, it is just a shorter barrel. So the volume you want to draw is fixed by the unit mark you pick, and the water volume follows from it:
Water mL = (units ÷ 100) × vial mg ÷ dose mg
Worked example, matching the defaults above. A 10 mg vial, a 250 mcg dose, and you want that dose to land on the 5-unit mark. 5 units is 0.05 mL. 250 mcg is 0.25 mg. So the water is 0.05 × 10 ÷ 0.25 = 2 mL, giving 5 mg/mL, 50 mcg per unit, and a 250 mcg dose that reads as exactly 5 units. Aim for the 20-unit mark instead and the water becomes 0.20 × 10 ÷ 0.25 = 8 mL. That is more than a vial holds: like the Dosify Me app, the calculator takes at most 3 mL of bacteriostatic water, so it refuses that target and asks for a lower one.
That is the whole trade-off: more water means a weaker mix and a bigger, easier-to-read number of units for the same dose. The amount of compound in the dose does not change.
Going the other way — you already added the water and want the syringe reading — use the reconstitution calculator, or a per-compound page for vial sizes already filled in.
This is a calculator for tracking, not guidance. It converts numbers you enter; it does not recommend a dose, a volume, or a schedule, and it is not a substitute for a qualified professional. Informational use only. Check every reading against your own product's instructions.
There is no single correct volume. The water decides the concentration, and the concentration decides the syringe reading — so the useful way to choose is backwards, from the unit mark you want to draw. That is what the calculator above does.
No. It changes the concentration, and therefore the number of units you draw — not the amount of compound in the dose. More water, weaker mix, larger unit reading, same dose.
0.01 mL. 100 units = 1 mL, 50 units = 0.5 mL.
Insulin syringes are marked in whole units. A mix that puts your dose at 7.3 units has to be eyeballed between marks every single time; a mix that puts it at 5 or 10 units reads straight off the barrel.
Dosify Me does this math for you. Pick the compound, your vial size and dose, and the app draws the exact syringe reading, keeps your schedule and reminders, and logs every dose — privately, on your phone.
Reconstitution calculator · How to reconstitute peptides · How much BAC water for a 5 mg vial · Per-compound dosing reference
New compound cards and revised reconstitution data go out in an occasional email — sign up on the home page. Reference material only, no promotions.