For most clinical laboratory applications, a concentration can be defined as the amount of a substance divided by the total volume of the mixture.
- An increasing concentration either reflects an increasing amount of substance with a fixed total volume or a decreasing total volume with a fixed amount of substance.
- A decreasing concentration either reflects a decreasing amount of substance with a fixed total volume or an increasing total volume with a fixed amount of substance.
Although many concentrations are described as the mass of a solute in a volume of solvent, molarity defines a concentration as the number of moles of solute in 1 liter of solution.
In the clinical laboratory, both mass/volume and molarity are used commonly to describe concentrations. Examples of how concentrations may be presented:
- grams per liter (g/L)
- milligrams per deciliter (mg/dL)
- cells per milliliter (cells/mL)
- nanomoles per milliliter (nmol/mL)
- units per milliliter (U/mL)
