Which unit is used to express creatinine clearance in practice?

Which unit is used to express creatinine clearance in practice?

• A. L/min
• B. mL/min
• C. mg/dL
• D. mol/L

Answer: (B)

Creatinine clearance measures how much plasma is cleared of creatinine per unit time, so its unit must be a rate of volume per time. In practice this is expressed as milliliters per minute (mL/min) because it represents the volume of plasma cleared every minute. The standard calculation is C = (urine creatinine concentration × urine flow rate) / plasma creatinine concentration, which results in a rate measured in mL/min. Other units like L/min would imply larger flow rates not typical for kidney clearance, and mg/dL or mol/L are concentrations, not clearance rates.

Creatinine clearance measures how much plasma is cleared of creatinine per unit time, so its unit must be a rate of volume per time. In practice this is expressed as milliliters per minute (mL/min) because it represents the volume of plasma cleared every minute. The standard calculation is C = (urine creatinine concentration × urine flow rate) / plasma creatinine concentration, which results in a rate measured in mL/min. Other units like L/min would imply larger flow rates not typical for kidney clearance, and mg/dL or mol/L are concentrations, not clearance rates.