Understanding Blood Urea Nitrogen: Normal vs Optimal Ranges

?What is Blood Urea Nitrogen?

Blood urea nitrogen (BUN) measures the amount of nitrogen in the blood in the form of urea. It is a common measure of kidney function and protein metabolism in Western labs. BUN = Urea × 0.467. Indian labs often report urea rather than BUN — conversion is needed when comparing across laboratories.

!Why It Matters

BUN is used alongside creatinine to calculate the BUN/creatinine ratio, which helps distinguish the cause of elevated kidney markers (pre-renal vs renal vs post-renal). A BUN/creatinine ratio above 20 suggests dehydration or reduced kidney perfusion; below 10 may indicate malnutrition.

Reference Ranges

Lab normal ranges may vary between laboratories. Optimal and longevity targets are based on research literature and should be interpreted with your physician.

Symptoms of Imbalance

• Similar to urea — mild elevation usually asymptomatic

How to Improve Your Levels

• 1Same as for urea and creatinine — address underlying cause

When to Test

Standard kidney function panel.

Related Biomarkers