How do I convert a peptide dose to units?

First find your concentration: vial amount in mg divided by the mL of water added. Then divide your target dose by the amount per unit. On a U-100 syringe, amount per unit in mcg equals concentration in mg per mL times 10. For example, a 5 mg vial in 2 mL water is 2.5 mg per mL, or 25 mcg per unit, so a 250 mcg dose is 10 units.

Peptide Encyclopedia / How many units is my dose

Guide

How many units is my peptide dose?

Q: Is a unit the same as a milligram?

No. A unit on a U-100 insulin syringe is a measure of volume, equal to 0.01 mL. Your dose in mg or mcg depends on how concentrated your vial is, which is set by how much bacteriostatic water you added when reconstituting.

Q: Why did my dose change when I added more water?

Adding more bacteriostatic water makes the solution more dilute, so each unit on the syringe holds less peptide. The same number of units then delivers a smaller dose. The peptide amount in the vial does not change, only the concentration.

This is the single most common way people get peptide dosing wrong. Units and milligrams are not the same thing, and mixing them up is how someone ends up drawing ten times too much. Here is the simple version.

The core idea: a "unit" is a measure of volume, not dose. The same 10 units can be a tiny dose or a large one depending on how you reconstituted the vial.

What a unit actually is

Peptides are usually drawn with a U-100 insulin syringe. On that syringe, 100 units = 1 mL, so 1 unit = 0.01 mL. The unit marks tell you how much liquid you are drawing, not how many milligrams of peptide are in it.

The one formula

Concentration = vial amount (mg) ÷ bacteriostatic water added (mL)

Amount per unit (mcg) = concentration (mg/mL) × 10

Units to draw = your dose (mcg) ÷ amount per unit (mcg)

The "× 10" shortcut works because one unit is 0.01 mL, and 0.01 mL of a mg/mL solution is 0.01 mg, which is 10 mcg per mg/mL.

Worked example (BPC-157)

You have a 5 mg vial and add 2 mL of bacteriostatic water.
Concentration = 5 ÷ 2 = 2.5 mg/mL.
Amount per unit = 2.5 × 10 = 25 mcg per unit.
You want a 250 mcg dose. Units = 250 ÷ 25 = 10 units.

Now change one thing: add 1 mL of water instead of 2. Concentration doubles to 5 mg/mL, each unit is now 50 mcg, and the same 250 mcg dose is only 5 units. The vial has the same peptide either way. Only the concentration, and therefore the units, changed.

Skip the mental math

Our free peptide dose converter does this both directions: type a dose in mg or mcg and get the units to draw, or type units and get the dose. If you are still deciding how much water to add, the reconstitution calculator helps you pick a concentration that gives round, easy-to-read numbers on the syringe.

Common mistakes to avoid

Reading "10 units" from someone else's protocol without knowing their concentration. Their 10 units is not your 10 units.
Assuming units equal micrograms. They do not.
Changing your water amount mid-vial without recalculating. Every unit now means a different dose.

Track it so you are not re-deriving this every time

PepWise stores your vial size, water added, and target dose, then shows the exact units to draw for each peptide and logs every dose with its injection site. Start free.

FAQ

Is a unit the same as a milligram?

No. A unit on a U-100 syringe is 0.01 mL of volume. The mg or mcg it contains depends on your concentration.

How do I convert a dose to units?

Concentration = vial mg ÷ water mL. Amount per unit (mcg) = concentration × 10. Units = dose ÷ amount per unit. A 5 mg vial in 2 mL is 25 mcg per unit, so 250 mcg is 10 units.

Why did my dose change when I added more water?

More water dilutes the solution, so each unit holds less peptide and the same units deliver a smaller dose.

PepWise is an informational and educational tracking tool, not medical advice and not a medical device. Always confirm your own dosing math and consult a licensed healthcare provider before starting, changing, or stopping any protocol. Operated by STC Consulting, Inc.