Urea (Ur)
Sample Type
Blood
Tube Type
Clot Tube
Fasting Required
No
Lab
Serum
Overview
Urea is a waste product formed in the liver from the breakdown of proteins and is excreted by the kidneys through urine. The blood urea test measures the concentration of urea nitrogen in the blood (commonly reported as Blood Urea Nitrogen, BUN, or simply Urea).
This test is primarily used to:
Assess kidney function
Monitor renal health in various diseases
Evaluate hydration status and protein metabolism
Detect renal failure, dehydration, or urinary tract obstruction
Test Result Interpretation
Urea Level (mg/dL) | Reference Range | Interpretation | Possible Causes |
|---|---|---|---|
Normal | 7 – 20 mg/dL (varies by lab) | Normal renal function and protein metabolism | Healthy kidneys and hydration |
Elevated (Azotemia) | > 20 mg/dL | Impaired kidney function or increased protein breakdown | Acute/chronic kidney disease, dehydration, high protein diet, gastrointestinal bleeding, heart failure |
Low | < 7 mg/dL | Possible liver disease or malnutrition | Severe liver disease (reduced urea synthesis), overhydration, low protein intake |
Risk Assessment
Urea levels can be affected by hydration status — dehydration raises urea concentration.
It is often interpreted alongside creatinine to assess renal function comprehensively.
Elevated urea with normal creatinine may indicate pre-renal causes such as dehydration.
Low urea is less common but can signal hepatic dysfunction or malnutrition.
Always correlate urea results clinically and with other renal parameters like creatinine, electrolytes, and glomerular filtration rate (GFR).