U-100 Syringe

A U-100 syringe is an insulin syringe calibrated so that 100 ‘units’ on the barrel equal 1 mL. Despite the term ‘unit,’ no actual unit of insulin is being measured — it is purely a volume scale at 1/100 mL per division.

U-100 syringes are the de-facto standard for subcutaneous peptide research because their fine 27- to 31-gauge needles minimize injection-site discomfort, and the 100-unit / 1-mL scale matches well to the typical 1–2 mg/mL concentrations used after reconstitution.

Sizes commonly used in research are 0.3 mL (30 units max, finest scale), 0.5 mL (50 units max), and 1 mL (100 units max). Choose the smallest size that fits the intended dose volume — finer scale means lower dose-error.