BUN to Creatinine Ratio Calculator
BUN:Creatinine Ratio
Calculate the BUN to creatinine ratio and estimate GFR.
mg/dL
mg/dL
years
Formula
BUN:Creatinine Ratio = BUN (mg/dL) / Creatinine (mg/dL). Normal: 10-20:1. eGFR (CKD-EPI 2021) = 142 × min(Cr/κ, 1)^α × max(Cr/κ, 1)^-1.2 × 0.9938^Age × Sex_factor.
Frequently Asked Questions
What is the BUN to creatinine ratio?
The BUN to creatinine ratio compares blood urea nitrogen to serum creatinine. Both are markers of kidney function, but they respond differently to various conditions. A normal ratio is between 10:1 and 20:1.
What does a high BUN to creatinine ratio mean?
A ratio above 20:1 suggests prerenal azotemia, where BUN rises disproportionately to creatinine. Common causes include dehydration, congestive heart failure, upper GI bleeding, high protein intake, and corticosteroid use. The kidneys retain more urea in low-flow states.
What does a low BUN to creatinine ratio mean?
A ratio below 10:1 may indicate intrinsic renal disease (e.g., acute tubular necrosis), liver disease (reduced urea production), malnutrition, rhabdomyolysis (elevated creatinine from muscle breakdown), or SIADH (dilutional effect).
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