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The Serum Urea test measures the concentration of urea — the primary nitrogen-containing waste product of protein metabolism —...
Also known as: Serum Urea Test · Blood Urea Test · Urea Nitrogen Test · BU Test
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*Inclusive of home collection charges
The Serum Urea test measures the concentration of urea — the primary nitrogen-containing waste product of protein metabolism — in your blood. The liver converts ammonia (produced when proteins are broken down) into urea, which the kidneys then filter out and excrete in urine. Rising blood urea levels signal declining kidney filtration capacity, making this one of the standard markers of kidney function included in the Renal Function Test (RFT) panel. No fasting required.
Key benefits of this package include:
What Does the Urea Test Measure?
| Level / Result | Possible Interpretation |
|---|---|
| 15–45 mg/dL (Normal) | Adequate kidney clearance of nitrogen waste |
| 45–80 mg/dL (Mildly elevated) | Possible dehydration, high-protein diet, or early kidney dysfunction — assess with creatinine |
| 80–150 mg/dL (Moderately elevated) | Significant kidney impairment — further evaluation and management required |
| > 150 mg/dL (Severely elevated — Uraemia) | Kidney failure — risk of uraemic complications; urgent medical attention |
| < 15 mg/dL (Low) | Possible liver disease (impaired urea production), malnutrition, or low-protein diet |
Important Note: Urea results must be interpreted alongside Creatinine (and the BUN:Creatinine ratio), eGFR, fluid status, dietary protein intake, and clinical symptoms. High urea with proportionally elevated creatinine suggests intrinsic kidney disease; high urea with relatively normal creatinine (high ratio) suggests a pre-renal cause like dehydration or upper GI bleeding.
The BUN:Creatinine Ratio — A Diagnostic Tool: When both BUN (or Urea) and Creatinine are elevated, calculating the ratio helps identify the cause. A BUN:Creatinine ratio above 20:1 suggests pre-renal azotaemia — dehydration, blood loss, heart failure, or upper GI bleeding — where the kidneys themselves are intact but receiving reduced blood flow. A ratio below 10–15:1 with elevated creatinine suggests intrinsic renal disease. This simple calculation from two routine tests substantially narrows the diagnostic differential.
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