# What is my peptide dose in units?

Does reconstitution arithmetic: the concentration after adding water to a vial, and the mL and syringe units (U-100, U-50, or U-40) for a dose you type. It has no drug presets and suggests no doses.

- Page: https://www.acalculator.org/health/peptide-calculator
- JSON spec: https://www.acalculator.org/health/peptide-calculator.json
- Version: 44e69e2763cd

## Default answer

Example with the default inputs (Amount in the vial (mg) 5, Water added (mL) 2, Dose unit mcg, Syringe U-100): The mixed vial holds 2.5 mg per mL, which is 25 mcg per syringe unit.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| mg | Amount in the vial (mg) | The milligrams of powder in the vial, as printed on the label. |
| ml | Water added (mL) | The milliliters of diluent (for example bacteriostatic water) added to the vial. |
| dose | Dose | Optional: the dose you were prescribed, in the unit chosen below. The calculator suggests none. |
| du | Dose unit | Whether the dose is in micrograms (mcg) or milligrams (mg). 1 mg = 1,000 mcg. |
| syr | Syringe | The syringe scale: U-100 has 100 units per mL, U-50 has 50, U-40 has 40. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| concentration | Concentration (mg/mL) | Milligrams of peptide in each mL after mixing, to 3 decimals. |
| perUnit | Per syringe unit (mcg) | Micrograms in one marked unit of the chosen syringe, to 2 decimals. |
| volume | Volume for the dose (mL) | The mL that hold the typed dose, to 3 decimals. Shown when a dose is typed. |
| units | Syringe units for the dose | The marked units to draw on the chosen syringe for the typed dose, to 1 decimal. |
| doses | Full doses in the vial | How many whole doses of the typed size the vial holds. |

## Method

Concentration (mg/mL) = vial mg ÷ water mL. Volume (mL) = dose (mg) ÷ concentration. Syringe units = volume × units per mL (100, 50, or 40).

## Assumptions

- The powder dissolves fully and adds no volume, the usual assumption for small peptide vials.
- The dose is the one you were prescribed; the calculator has no drug list and suggests no doses.
- Values are rounded for display, halves up; full doses round down.

## Worked examples

1. mg = 5, ml = 2, dose = 250, du = mcg, syr = u100 gives concentration = 2.5, perUnit = 25, volume = 0.1, units = 10, doses = 20. Source: × 100 units/mL (ISO 8537 U-100) = 10 units.
2. mg = 10, ml = 3, dose = 500, du = mcg, syr = u100 gives concentration = 3.333, perUnit = 33.33, volume = 0.15, units = 15, doses = 20.
3. mg = 5, ml = 1, dose = 1, du = mg, syr = u40 gives concentration = 5, perUnit = 125, volume = 0.2, units = 8, doses = 5.
4. mg = 2, ml = 1.5, dose = 0.25, du = mg, syr = u100 gives concentration = 1.333, volume = 0.188, units = 18.8, doses = 8.
5. mg = 5, ml = 2, du = mcg, syr = u50 gives concentration = 2.5, perUnit = 50.

## FAQ

### How do I calculate peptide reconstitution?

Divide the milligrams in the vial by the milliliters of water you add. A 5 mg vial mixed with 2 mL of water holds 5 ÷ 2 = 2.5 mg per mL, which is 2,500 mcg per mL.

### How many units on an insulin syringe is my dose?

First find the volume: dose ÷ concentration. Then multiply by the syringe scale. A U-100 syringe has 100 units in 1 mL, so each unit is 0.01 mL. For a 250 mcg dose from a 2,500 mcg/mL vial: 250 ÷ 2,500 = 0.1 mL = 10 units on a U-100 syringe.

### What is the difference between U-100, U-50, and U-40 syringes?

The number is how many marked units fit in 1 mL. On a U-100 syringe one unit is 0.01 mL; on a U-40 syringe one unit is 0.025 mL. The same dose is a different number of units on each scale, so use the scale that matches your syringe.

### Does the calculator tell me how much peptide to take?

No. It has no drug list and no suggested doses; it only turns a dose you were prescribed into mL and syringe units. Many peptides sold online are research chemicals, not approved medicines, and the US Food and Drug Administration has warned that some bulk peptides may present significant safety risks.

### Does the powder change the volume?

For the small amounts in peptide vials the powder adds almost no volume, so the calculator treats the volume as the water you added. This is the usual assumption.

## Sources

- International Organization for Standardization. ISO 8537:2016, Sterile single-use syringes, with or without needle, for insulin (U-40 and U-100 scales). https://www.iso.org/standard/60510.html
- Gage CB, Preuss CV. Dose Calculation. In: StatPearls. StatPearls Publishing; 2023. https://www.ncbi.nlm.nih.gov/books/NBK430836/ (retrieved 2026-09-29)
- US Food and Drug Administration. Certain bulk drug substances for use in compounding that may present significant safety risks. https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks (retrieved 2026-09-29)