Blood Urea Nitrogen (BUN): A waste product formed from protein metabolism, excreted by the kidneys.

Creatinine: A breakdown product of muscle metabolism, filtered by the kidneys at a relatively constant rate.

The ratio of BUN to creatinine provides insight into kidney function and systemic conditions.

Clinical uses include:

Differentiating pre‑renal azotemia (dehydration, shock, heart failure) from intrinsic renal disease.

Evaluating post‑renal obstruction (stones, tumors).

Monitoring patients with chronic kidney disease (CKD).

Assessing hydration status and protein metabolism.

Analyte: Ratio of BUN (mg/dL) to creatinine (mg/dL) in serum.

Normal Range: ~10:1 to 20:1 (varies by lab).

Abnormal Findings:

High ratio (>20:1): Suggests pre‑renal causes (dehydration, reduced blood flow to kidneys, GI bleeding).

Low ratio (<10:1): Suggests intrinsic renal disease or liver disease.

Normal ratio with elevated values: May indicate post‑renal obstruction.

Clinical Use:

Provides a quick assessment of kidney function and systemic status.

Helps differentiate causes of elevated urea and creatinine.

Guides further renal and metabolic investigations.