This article is for educational and research purposes only. Nothing here constitutes medical advice. Dosing should only be determined by a licensed healthcare provider.
Why Units Cause Confusion
One of the most common sources of confusion for peptide beginners is the mix of measurement units used across different peptides, vendors, and community discussions. A single conversation might reference micrograms, milligrams, international units, and insulin syringe units — all for the same peptide. Understanding the relationships between these units is essential for safe and accurate dosing.
Weight-Based Units
- Milligram (mg): One thousandth of a gram. Peptide vial contents are usually listed in milligrams (e.g., a 5 mg vial of BPC-157).
- Microgram (mcg or μg): One millionth of a gram, or one thousandth of a milligram. Most peptide doses are measured in micrograms. 1 mg = 1,000 mcg.
- Example: If a protocol calls for 250 mcg of BPC-157, that is 0.25 mg. From a 5 mg vial, that dose represents 1/20th of the total vial contents.
Volume Units
- Milliliter (mL): A unit of volume. When you reconstitute a peptide with bacteriostatic water, you choose how many mL to add. This determines the concentration of the solution.
- Units on an insulin syringe: Insulin syringes are marked in "units" — a 100-unit (1 mL) insulin syringe means 100 units = 1 mL. Each "unit" on the syringe equals 0.01 mL. This is a volume measurement, not a dose measurement.
International Units (IU)
International Units are a standardized measure of biological activity, not weight. They are most commonly used for HGH (human growth hormone), insulin, and some vitamins. The conversion between IU and milligrams depends on the specific substance. For HGH, 1 mg equals approximately 3 IU, but this ratio does not apply to other peptides. Do not attempt to convert IU to mg for one compound based on another compound's ratio.
Putting It Together
Here is a practical example. You have a 5 mg vial of a peptide and reconstitute it with 2 mL of bacteriostatic water:
- Concentration = 5 mg / 2 mL = 2.5 mg/mL = 2,500 mcg/mL
- If your dose is 250 mcg, you need 0.1 mL (or 10 units on an insulin syringe)
- 250 mcg ÷ 2,500 mcg/mL = 0.1 mL = 10 units on a 100-unit syringe
Always double-check your math before drawing. A 10x dosing error can happen easily if you confuse mg and mcg, or miscalculate the concentration after reconstitution. Many people use online peptide reconstitution calculators to verify their math, which is a sensible precaution.
The Golden Rule
When in doubt, recheck. Dosing errors are one of the most preventable risks in peptide use. Write down your reconstitution math, label your vials with the concentration, and verify every calculation before injecting.