Uric acid comprises what percent of non-protein nitrogen (NPN)?

• A. 1-5%
• B. 5-10%
• C. 10-20%
• D. 30-40%

Answer: (C)

Non-protein nitrogen means the nitrogen-containing waste products in body fluids that are not proteins, such as urea, uric acid, creatinine, ammonia, and amino acids. Uric acid is one of these components, but it isn’t the dominant one; the major portion of NPN is typically urea. In many clinical references, uric acid accounts for about ten to twenty percent of the total non-protein nitrogen. So the range of ten to twenty percent best fits how much uric acid contributes to NPN. Narrower or larger ranges would not reflect its usual proportion.