What is the normal BUN/creatinine ratio?

A normal BUN/creatinine ratio is typically 10:1 to 20:1. Ratios above 20 suggest pre-renal causes (dehydration, GI bleeding, heart failure). Ratios below 10 suggest intrinsic renal disease, malnutrition, or liver disease.

What does a high BUN/creatinine ratio mean?

A ratio above 20 generally indicates pre-renal azotemia — conditions that reduce renal perfusion such as dehydration, hemorrhage, heart failure, or high protein catabolism (e.g., GI bleeding). The kidneys are functioning but receiving less blood flow.

What does a low BUN/creatinine ratio mean?

A ratio below 10 can indicate intrinsic renal disease (glomerulonephritis, acute tubular necrosis), low protein intake, severe liver disease reducing urea synthesis, or rhabdomyolysis with disproportionate creatinine rise.

What units should I use for BUN and creatinine?

This calculator uses mg/dL for both BUN and creatinine, which is standard in the United States. If your lab reports in mmol/L, convert: BUN (mg/dL) = BUN (mmol/L) × 2.8; Creatinine (mg/dL) = Creatinine (µmol/L) ÷ 88.4.

Can this calculator diagnose kidney disease?

No. The BUN/creatinine ratio is one of many diagnostic tools. Always interpret results in the full clinical context including history, physical exam, urinalysis, and other lab values. This tool is for educational reference only.

BUN/Creatinine Ratio Calculator

Name: BUN/Creatinine Ratio Calculator
Availability: InStock
Author: Nham Vu

Enter BUN and serum creatinine values to calculate the ratio and get a clinical interpretation of the likely cause of renal dysfunction.

Lab Values

BUN — Blood Urea Nitrogen (mg/dL)

Serum Creatinine (mg/dL)

Reference Ranges

Normal BUN7–25 mg/dL

Normal Creatinine (male)0.7–1.3 mg/dL

Normal Creatinine (female)0.5–1.1 mg/dL

Result

Enter lab values and click Calculate

Summary

Enter BUN and serum creatinine values to calculate the ratio and get a clinical interpretation of the likely cause of renal dysfunction.

How it works

Enter the Blood Urea Nitrogen (BUN) value in mg/dL.
Enter the serum creatinine value in mg/dL.
Click Calculate to compute the ratio.
Review the numeric ratio and clinical interpretation.
Use the interpretation to guide further clinical workup.

Use cases

Differentiate pre-renal azotemia from intrinsic kidney disease.
Assess acute kidney injury etiology in hospitalized patients.
Evaluate dehydration and volume depletion effects on renal labs.
Screen for gastrointestinal bleeding as a cause of elevated BUN.
Monitor renal function trends in patients with chronic kidney disease.
Guide fluid resuscitation decisions in patients with elevated creatinine.

Frequently Asked Questions

Last updated: 2026-07-22 · Reviewed by Nham Vu