Peptide Dosage Reference: Units, mcg, mg

How do peptide dosage units work — mcg, mg, mg/ml, U-100 units?

Peptide dosage uses four unit systems that convert into each other: mass (mcg or mg), volume (ml), concentration (mg/ml), and syringe units (U-100 or U-40). 1 mg = 1,000 mcg. Concentration = vial mass ÷ BAC water. Draw volume = target dose ÷ concentration. U-100 units = draw volume × 100. Peptly does these conversions live.

Unit reference

• mcg (microgram) — 1/1,000 of a mg. Common for small-dose research peptides (e.g. BPC-157 at 250 mcg).
• mg (milligram) — common for GLP-1 / GIP-GLP-1 peptide dosing (e.g. semaglutide at 0.25 mg).
• ml (milliliter) — volume drawn into the syringe.
• mg/ml (concentration) — how much peptide mass is in each ml of reconstituted solution.
• U-100 unit — 0.01 ml. 100 units fills a 1 ml U-100 syringe.
• U-40 unit — 0.025 ml. 40 units fills a 1 ml U-40 syringe.

Conversion formulas

1. mcg → mg: divide by 1,000.
2. mg → mcg: multiply by 1,000.
3. Concentration: vial mass (mg) ÷ BAC water (ml) = mg/ml.
4. Draw volume: target dose (mg) ÷ concentration (mg/ml) = ml.
5. U-100 units: ml × 100.
6. U-40 units: ml × 40.

Common error patterns

• mg / mcg mix-up. A 250 mg dose is 1,000× a 250 mcg dose. Always verify units.
• U-100 / U-40 mix-up. 10 units on U-100 (0.1 ml) is far less than 10 units on U-40 (0.25 ml).
• Stale concentration. If you change BAC water volume mid-cycle, the saved mix is no longer valid.
• Inconsistent decimal handling. 0.25 mg is the same as 250 mcg — Peptly shows both representations to avoid confusion.

See also

• Main peptide calculator
• Reconstitution math reference
• BAC water calculator
• How to reconstitute peptides

Frequently asked questions

What is the difference between mcg and mg? +

1 mg = 1,000 mcg. mcg is microgram, mg is milligram. The factor of 1,000 between them is the most common source of error in reconstitution math — Peptly always shows the unit explicitly to avoid ambiguity.

How do I convert mg/ml to U-100 units? +

U-100 units = draw volume (ml) × 100. To get the draw volume, divide the target dose (mass) by the concentration (mg/ml). Example: 250 mcg at 2.5 mg/ml = 0.1 ml = 10 units on U-100.

What is a U-100 syringe? +

A U-100 insulin syringe is scaled so that 100 units = 1 ml. Each unit mark represents 0.01 ml. This is the most common reference scale in research peptide use.

What is the difference between U-100 and U-40? +

U-100 has 100 units per ml (1 unit = 0.01 ml). U-40 has 40 units per ml (1 unit = 0.025 ml). The same number of units on different scales is a different volume. Peptly defaults to U-100; U-40 is a setting.

Does Peptly recommend dosing? +

No. Peptly is a calculator and reference tool. Values shown are arithmetic outputs — not medical advice, not dosing recommendations. Consult a licensed clinician before any injection.