If BUN is high but creatinine is normal, what interpretation is most likely?

• A. Acute kidney injury
• B. Dehydration with preserved kidney function
• C. Liver disease
• D. Anemia

Answer: (B)

The situation relies on how BUN and creatinine reflect kidney function and volume status. When you’re dehydrated, blood flow to the kidneys drops, so the kidneys conserve water by reabsorbing more urea (BUN) in the tubules. This raises the BUN level, but if kidney filtration (GFR) is still preserved, creatinine stays normal. So a high BUN with a normal creatinine most likely points to dehydration with preserved kidney function.

This fits better than the other possibilities: acute kidney injury would typically push creatinine up because filtration is reduced. Liver disease tends to lower BUN production, so BUN wouldn’t be elevated. Anemia doesn’t directly cause a rise in BUN, since it doesn’t reflect kidney clearance or urea production in the same way.