By what factor does BUN convert to urea?

By what factor does BUN convert to urea?

• A. ×2.14
• B. ×1.8
• C. ×1.0
• D. ×3.0

Answer: (A)

BUN reflects only the nitrogen portion of the urea molecule, not the total urea mass. To get the actual urea concentration from BUN, use the ratio of urea’s molecular weight to the nitrogen content: urea has a molar mass of about 60.06 g/mol and contains about 28.02 g of nitrogen per mole. Dividing 60.06 by 28.02 gives 2.14. So multiply the BUN value by 2.14 to estimate urea concentration. This works because nitrogen makes up roughly 46.6% of urea by weight. For example, a BUN of 20 mg/dL corresponds to about 42.8 mg/dL of urea.

BUN reflects only the nitrogen portion of the urea molecule, not the total urea mass. To get the actual urea concentration from BUN, use the ratio of urea’s molecular weight to the nitrogen content: urea has a molar mass of about 60.06 g/mol and contains about 28.02 g of nitrogen per mole. Dividing 60.06 by 28.02 gives 2.14. So multiply the BUN value by 2.14 to estimate urea concentration. This works because nitrogen makes up roughly 46.6% of urea by weight. For example, a BUN of 20 mg/dL corresponds to about 42.8 mg/dL of urea.