Urea (BUN)
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About This Test
Urea (often reported as BUN) is a waste product made in the liver from protein breakdown and cleared by the kidneys. When kidneys don’t filter well—or when you’re dehydrated—urea can rise. Low levels are less common and may reflect severe liver disease or very low protein intake. Doctors read urea together with creatinine and electrolytes to understand kidney function and hydration. This test is commonly included in routine chemistry panels to detect problems early.
Patient Preparation
No fasting needed. If possible, avoid high-protein binges and heavy exercise the day before.
Best Time to Test
Anytime
Tests Included
Urea
Why is it done
Evaluation of fatigue, swelling, or reduced urine output; monitoring chronic kidney disease or dehydration; assessing effects of high-protein diets, GI bleeding, or certain medicines (e.g., diuretics); pre-procedure checks and routine screening alongside creatinine.