What is the reference range for ammonia in micrograms per deciliter?

• A. 5-15
• B. 19-60
• C. 60-120
• D. 100-200

Answer: (B)

Ammonia in blood is a waste product that the liver normally detoxifies, so the reference range is based on healthy individuals with normal liver function. In many clinical labs, the normal range for plasma ammonia is around 15–60 µg/dL, though exact cutoffs can vary with the assay and handling.

The option 19–60 µg/dL falls within this commonly cited range, making it the best match among the choices. Remember, accurate ammonia measurement requires careful handling (keep samples on ice, rapid processing, avoid hemolysis) because levels can rise or fall with time, meals, or improper handling. Elevated ammonia suggests hepatic dysfunction, urea-cycle disorders, or other conditions that impair ammonia clearance.