Math & Measurement
Concentration
Definition
The amount of a substance contained in a given volume of liquid, such as mg/mL or mcg/mL.
What Concentration means
Concentration connects the amount in a vial to the liquid volume. If the same vial amount is dissolved in more liquid, the concentration becomes lower; if it is dissolved in less liquid, the concentration becomes higher.
Why the distinction matters
BACToBasics calculators use concentration as the bridge between vial amount, liquid volume, and the volume represented by a syringe draw.
Common confusion
Concentration is not the same thing as a dose or a syringe-unit marking. It describes how much substance is present per unit of liquid volume.
See this concept in context
Open the BACToBasics tools and reference pages where this term is used.
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Related glossary terms
Math & Measurement
Milligram (mg)
A unit of mass equal to one-thousandth of a gram.
Math & Measurement
Microgram (mcg)
A unit of mass equal to one-millionth of a gram, or one-thousandth of a milligram.
Math & Measurement
Milliliter (mL)
A metric unit of liquid volume equal to one-thousandth of a liter.
Math & Measurement
U-100 Syringe Units
Volume markings on a U-100 insulin syringe where 100 units correspond to 1 mL of liquid.
Reconstitution & Vials
Reconstitution
The process of adding a liquid to a dry or lyophilized product so that it becomes a solution or suspension with a calculable concentration.
Published September 6, 2026. BACToBasics glossary pages are educational definitions only and do not provide medical, dosing, preparation, treatment, or product-selection advice.