How much bacteriostatic water do I add to a 10 mg PT-141 vial?

There is no single right amount. More water makes each draw bigger and easier to measure; less water keeps the volume small. With 2 mL, a 10 mg vial is 5 mg/mL, so every 10 units on a U-100 insulin syringe holds 500 mcg. With 1 mL it is 10 mg/mL (1 mg per 10 units). With 3 mL it is 3.33 mg/mL (333.333 mcg per 10 units). With 5 mL it is 2 mg/mL (200 mcg per 10 units).

How many units is 1.75 mg of PT-141 from a 10 mg vial?

With 2 mL of water the vial is 5 mg/mL, so 1.75 mg is 0.35 mL, or 35 units on a U-100 syringe. With a different water volume the units change but the amount does not. The amount is an example for the math, not a recommendation.

How many 1.75 mg draws are in a 10 mg PT-141 vial?

5.7 (10 mg ÷ 1.75 mg), whatever volume of water you add. In practice a little is lost to the syringe dead space and the last drops in the vial.

PT-141 10 mg Reconstitution: BAC Water & Units

Short answer: 2 mL of bacteriostatic water in a 10 mg PT-141 vial makes 5 mg/mL. On a U-100 insulin syringe (1 mL = 100 units), every 10 units then holds 500 mcg. More water gives a weaker solution and a bigger draw for the same amount; the amount in the vial stays 10 mg.

Water volume chart for a 10 mg vial

10 mg PT-141 vial, U-100 insulin syringe.
Water added	Concentration	Per 10 units	Per 1 unit
1 mL	10 mg/mL	1 mg	100 mcg
2 mL	5 mg/mL	500 mcg	50 mcg
3 mL	3.33 mg/mL	333.333 mcg	33.333 mcg
5 mL	2 mg/mL	200 mcg	20 mcg

Syringe units by amount

The amounts below are examples to show the conversion, not doses. How much to take is a decision for you and your prescriber.

Units on a U-100 syringe from a 10 mg vial.
Water added	875 mcg	1.75 mg	3.5 mg
1 mL	8.8 units	17.5 units	35 units
2 mL	17.5 units	35 units	70 units
3 mL	26.3 units	52.5 units	over 1 mL
5 mL	43.8 units	87.5 units	over 1 mL

A 10 mg vial holds 11.4 draws of 875 mcg, 5.7 draws of 1.75 mg, 2.9 draws of 3.5 mg, no matter how much water you add.

How far a 10 mg vial goes

Draws per vial depend only on the amount per draw, not on the water. The volume and units columns use 2 mL of water (5 mg/mL). Example amounts only, not doses.

10 mg vial: draws, volume and units per example amount.
Amount per draw	Draws per vial	Volume per draw	Units per draw
437.5 mcg	22.9	0.088 mL	8.8 units
875 mcg	11.4	0.175 mL	17.5 units
1.75 mg	5.7	0.35 mL	35 units
3.5 mg	2.9	0.7 mL	70 units
7 mg	1.4	1.4 mL	over 1 mL

Real counts run a little lower: some liquid stays in the syringe and at the bottom of the vial.

The math

Concentration. 10 mg ÷ 2 mL = 5 mg/mL
Volume to draw. amount ÷ 5 mg/mL = mL
Syringe units. mL × 100 = units

For a different water volume or amount, the free peptide reconstitution calculator works backwards from the amount you want and suggests a water volume that lands on a clean syringe mark.

Half-life, time to peak and sources are on the main PT-141 (Bremelanotide) guide.

PT-141 10 mg reconstitution: how much water and how many units

Water volume chart for a 10 mg vial

Syringe units by amount

How far a 10 mg vial goes

The math

Frequently asked questions