BUN to Creatinine Ratio Calculator

mg/dL
mg/dL
Health Updated 14 Jun 2026

Calculate the BUN-to-creatinine ratio from your blood urea nitrogen and serum creatinine values — a lab ratio used to help distinguish causes of kidney dysfunction. Enter both lab values in mg/dL to get the ratio and a general interpretation.

Rates and fees change frequently. Always confirm the current figures with the official authority before relying on this result.
  • Interpretive aid only. Requires physician evaluation in clinical context.

Formula

Ratio = BUN ÷ serum creatinine (both in mg/dL)
  • The ratio divides blood urea nitrogen (BUN) by serum creatinine, both measured in mg/dL.
  • A normal ratio is roughly 10:1 to 20:1.
  • A high ratio (>20:1) often points to a pre-renal cause such as dehydration or bleeding.
  • A low ratio (<10:1) can suggest intrinsic kidney disease or low protein intake.
  • It's an interpretive aid only — results must be reviewed by a clinician alongside the full clinical picture.

BUN 15, creatinine 1.0

Inputs
  • Blood urea nitrogen (BUN): 15 mg/dL
  • Serum creatinine: 1 mg/dL

15 ÷ 1.0 = 15:1, which falls in the normal 10–20 range.

Frequently asked questions

What is the BUN-to-creatinine ratio?
It compares blood urea nitrogen to serum creatinine and helps doctors work out why kidney function markers are abnormal.
What is a normal BUN:creatinine ratio?
Roughly 10:1 to 20:1, though reference ranges vary slightly between laboratories.
What does a high ratio mean?
A ratio above 20:1 commonly suggests a pre-renal cause like dehydration, blood loss, or reduced kidney blood flow.
What does a low ratio mean?
A ratio below 10:1 can indicate intrinsic kidney damage, low protein intake, or liver disease.
Can I diagnose kidney disease with this?
No. It's one clue among many. A clinician interprets it with other tests and your symptoms.

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