Valproic acid levels are measured in which units?

• A. mg/dL
• B. ng/mL
• C. mcg/mL
• D. mmol/L

Answer: (C)

Valproic acid levels are measured in micrograms per milliliter because the drug’s therapeutic concentrations in blood fall in the tens to hundreds of micrograms per milliliter range, and clinical labs report results in this unit for easy interpretation. Using mcg/mL aligns with the typical therapeutic window (roughly around 50–100 mcg/mL) and keeps conversions simple for daily practice. Other units would either obscure the usual range or require extra conversions: mg/dL would imply values that don’t map as directly to common therapeutic levels, ng/mL would represent much smaller concentrations than what’s clinically relevant for this drug, and mmol/L would necessitate converting by the drug’s molecular weight and isn’t standard for valproate monitoring. Hence, mcg/mL is the conventional, practical unit for valproic acid plasma levels.