Math & Measurement
U-100 Syringe Units
Also called: syringe units, U-100 units, insulin syringe units
Definition
Volume markings on a U-100 insulin syringe where 100 units correspond to 1 mL of liquid.
What U-100 Syringe Units means
A U-100 syringe divides 1 mL into 100 equal volume markings. That means 10 units represents 0.1 mL, 25 units represents 0.25 mL, and 50 units represents 0.5 mL.
Why the distinction matters
BACToBasics converts between mL and U-100 markings only after the vial concentration is known. The syringe marking itself does not tell you how many mg or mcg are present.
Common confusion
The word “units” on a U-100 syringe refers to the syringe scale. It should not be treated as a universal dose unit or confused with International Units (IU).
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Related glossary terms
Math & Measurement
Milliliter (mL)
A metric unit of liquid volume equal to one-thousandth of a liter.
Math & Measurement
Concentration
The amount of a substance contained in a given volume of liquid, such as mg/mL or mcg/mL.
Math & Measurement
International Unit (IU)
A substance-specific unit of biological activity that cannot be converted generically to mg or mcg.
Published September 6, 2026. BACToBasics glossary pages are educational definitions only and do not provide medical, dosing, preparation, treatment, or product-selection advice.