In a 24-hour urine protein test, the amount excreted is commonly expressed as which unit?

• A. mg/day
• B. mg/dL
• C. g/day
• D. μg/min

Answer: (A)

The main idea is that a 24-hour urine protein test reports the total amount of protein excreted over an entire day, not a concentration at a single moment. Because you’re summing everything excreted in 24 hours, the natural and widely used unit is milligrams per day. This makes the result straightforward to interpret as a daily protein load, with standard clinical thresholds expressed in mg/day (such as normal <150 mg/day, microalbuminuria 30–300 mg/day, nephrotic-range >3.5 g/day).

Using a concentration like mg/dL would require knowing the total urine volume to convert to a daily total, which is unnecessary for the standard reporting of a 24-hour collection. A unit like μg/min represents a rate, not a daily total, and while you could convert it to daily excretion, mg/day is the conventional, clinically meaningful expression. Similarly, while grams per day could technically convey the same information, mg/day is more commonly used because the usual daily protein excretion values fall in the milligram range, making reports more precise and conventional.