Nitrogen balance assessment: urinary urea nitrogen accounts for what percentage of total urinary nitrogen losses?

• A. 60%
• B. 80%
• C. 50%
• D. 70%

Answer: (B)

In nitrogen balance assessment, most nitrogen is excreted in urine as urea, which comes from the breakdown of amino acids. Urinary urea nitrogen accounts for about four-fifths of total urinary nitrogen losses, roughly 80%. The remaining 20% comes from other urinary nitrogen forms such as ammonium, creatinine, and uric acid. Because of this, UUN is a practical proxy for total urinary nitrogen, and a common conversion is to estimate total urinary nitrogen as UUN multiplied by 1.25 (or UUN divided by 0.8).