Tesamorelin Bac Water Ratio Guide

The bac water ratio is the amount of bacteriostatic water added to a tesamorelin vial relative to the peptide mass inside it, and it is the single number that sets concentration, draw volume, and the syringe reading for every dose that follows. This reference explains how to choose a tesamorelin bac water ratio, convert it into a concentration, and read the result in units on a U-100 insulin syringe. It is written for research purposes only and is not medical advice.

What a bac water ratio means

A bac water ratio is usually written as water volume per unit of peptide mass — "1 mL per 10 mg," for example. That ratio fixes the concentration the moment the powder dissolves, and concentration is what turns a target dose into a specific syringe reading. Two tesamorelin vials holding the identical amount of peptide can require completely different draw volumes if they were mixed with different amounts of bacteriostatic water. The ratio is set once, at reconstitution, so it is worth checking against the calculator before mixing rather than after.

The reference ratio for tesamorelin

Tesamorelin is commonly reconstituted at a ratio that scales water to vial size — 1 mL of bacteriostatic water per 10 mg of peptide. That ratio holds the concentration at a constant 10 mg/mL regardless of which vial size you're working from:

Vial size	Water added	Concentration
10 mg	1 mL	10 mg/mL
20 mg	2 mL	10 mg/mL
30 mg	3 mL	10 mg/mL

Because the ratio scales with vial size, the units for any given dose stay the same across all three sizes — only the number of total doses the vial holds changes. Nothing requires this exact ratio. A smaller water volume concentrates the dose into a smaller draw, which can be harder to measure accurately on a syringe. A larger water volume spreads the same dose across a bigger draw, which is generally easier to read but empties the vial faster.

Turning a ratio into syringe units — the math

The bac water ratio becomes a usable number in three steps.

Step 1: Concentration = vial mass ÷ water volume. A 20 mg tesamorelin vial with 2 mL of bacteriostatic water added is 20 ÷ 2 = 10 mg/mL.

Step 2: Volume = dose ÷ concentration. A 1 mg dose at 10 mg/mL concentration is 1 ÷ 10 = 0.1 mL.

Step 3: Units = volume (mL) × 100. On a U-100 insulin syringe, 1 mL equals 100 units, so 0.1 mL × 100 = 10 units.

The same three steps apply to any tesamorelin vial and ratio. A 30 mg vial reconstituted with 3 mL of water is also 30 ÷ 3 = 10 mg/mL, so a 1.5 mg dose from that vial is 1.5 ÷ 10 = 0.15 mL, or 15 units.

Rather than working through this by hand for every vial and dose, enter the numbers into the peptide reconstitution calculator and it returns the concentration and unit reading directly.

Picking a ratio in reverse, to land on a clean syringe reading

Sometimes the more useful question runs the other way: given a typical dose, what bac water ratio produces a syringe reading that's easy to draw and double-check? Take a 30 mg vial and a target dose of 2 mg. To land that dose on exactly 20 units (0.2 mL), the concentration needs to be dose ÷ volume = 2 ÷ 0.2 = 10 mg/mL. Working backward, water volume = vial mass ÷ concentration = 30 ÷ 10 = 3 mL. Reconstituting that 30 mg vial with 3 mL of bacteriostatic water puts a 2 mg dose exactly on the 20-unit mark. The free peptide calculator runs this reverse calculation directly — enter the vial size, target dose, and desired unit reading, and it returns the water volume that produces it.

Mixing steps

1. Gather the vial, bacteriostatic water, a U-100 insulin syringe, and alcohol swabs.
2. Swab the stopper of the vial with alcohol.
3. Draw the bac water volume your chosen ratio calls for.
4. Inject it slowly down the inside wall of the vial, not directly onto the powder.
5. Swirl gently until fully dissolved — do not shake.
6. Confirm the resulting concentration matches what you entered into the calculator before drawing a dose.

For the general steps that apply to any peptide vial, see how to reconstitute peptides.

Storage

Reconstituted tesamorelin is generally stored refrigerated and protected from light. Unreconstituted lyophilized powder is stable at room temperature until the expiration date on the vial. Track the date each vial was mixed — a reconstituted solution does not stay stable indefinitely, even refrigerated, and the ratio calculated at mixing time is only accurate for as long as the solution holds.

Common mistakes

• Reusing a bac water volume across a different vial size without recalculating. A ratio expressed as "1 mL per 10 mg" scales — 2 mL for a 20 mg vial, 3 mL for a 30 mg vial.
• Mixing up mg and mcg. Tesamorelin vials and doses are generally described in milligrams. 1 mg = 1000 mcg — confirm which unit a number refers to before it goes into the calculator.
• Shaking instead of swirling. Shaking can degrade the peptide; a gentle swirl is enough to dissolve it.
• Assuming a non-U-100 syringe. The unit conversions above hold only for a standard U-100 insulin syringe (100 units per mL).
• Confusing frequency with concentration. How often a dose is drawn does not change the ratio; only vial mass and water volume set concentration. See tesamorelin injection frequency research for how the two interact.

Use the calculator

Enter your tesamorelin vial size and a candidate bac water volume into the peptide dosage calculator to see the resulting ratio, concentration, and syringe units for any target dose, or run reverse mode to find the water volume that lands a chosen dose on a clean unit mark. For a closer look at the standard reconstitution setup and vial sizes, see the tesamorelin reconstitution calculator guide. The calculator handles the arithmetic; this guide explains what the ratio means before the water ever meets the powder.