Lab Values For Nurses Practice Test

The BUN/creatinine ratio helps distinguish hydration status and prerenal issues from intrinsic kidney problems. The typical range is about 10–20:1, so a ratio in this range is considered normal and not indicative of dehydration. A ratio of 18:1 fits within that normal band, reflecting balanced urea production and clearance. Dehydration can push this ratio higher because BUN tends to rise more than creatinine when renal perfusion is reduced and the body reabsorbs more urea to conserve water, so ratios often exceed 20:1 in prerenal states, though they’re not exclusively diagnostic. Very low ratios or specific nonnormal values (like a ratio around 30:1) are not considered normal for hydration assessment, reinforcing why the typical 10–20:1 range is the best descriptor for this context.