Syringe Markings Explained: Converting U-100, U-50, and U-30 Insulin Syringes to Micrograms

One of the most frequent sources of confusion in peptide literature analysis is the concept of syringe "units."

• 100 units = 1.0 mL
• 50 units = 0.50 mL
• 10 units = 0.10 mL
• 1 unit = 0.01 mL

Units Are a Measure of Volume, NOT Dose:
A syringe unit does not tell you how many milligrams (mg) or micrograms (mcg) of peptide you are administering until you factor in the concentration of the reconstituted solution.

The Three-Step Mathematical Rule:

Step 1: Calculate Total Concentration
Concentration (mg/mL) = Total Vial Mass (mg) / Volume of Added Liquid (mL)
Example: 5 mg vial reconstituted with 2.0 mL liquid = 2.5 mg/mL (or 2,500 mcg/mL).

Step 2: Calculate Required Volume for Reference Dose
Required Volume (mL) = Target Dose (mcg) / Concentration (mcg/mL)
Example: Target dose of 250 mcg / 2,500 mcg/mL = 0.10 mL.

Step 3: Convert Volume to Syringe Units
Syringe Units = Required Volume (mL) * 100
Example: 0.10 mL * 100 = exactly 10 units on a U-100 syringe.