U-100 syringes were designed for standard-strength insulin (100 international units per millilitre), which is why their scale is graduated in “units”. Outside that use, the unit marking only shows volume: 10 units are 0.1 mL; 25 units, 0.25 mL; 50 units, 0.5 mL.
How much peptide is in that volume depends on the concentration of the solution. With a 2 mg/mL solution, 10 units (0.1 mL) contain 0.2 mg; with the same syringe and a 5 mg/mL solution, the same 10 units contain 0.5 mg. That is why reconstitution tables always relate solvent volume, resulting concentration and unit equivalence.
There are syringes of other capacities (0.3, 0.5 and 1 mL) with the same U-100 scale, which allow small volumes to be measured with greater resolution.
Confusing syringe “units” with international units of activity (such as those of HGH) or with milligrams is a classic mistake. A syringe unit is always 0.01 mL.
Related terms
Learn it in depth at the Peptide University
- Practical calculation cases and common errors · Module 9
- The arithmetic of concentration · Module 9
- Technical fundamentals of subcutaneous administration · Module 8
- Physical degradation: aggregation and adsorption · Module 11
Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).