About this calculator
The BUN/creatinine ratio is a simple lab ratio sometimes used to frame kidney and volume-status patterns. It is nonspecific and must be interpreted with clinical context.
Source-backed
BUN/creatinine ratio = BUN ÷ serum creatinine. Ratios above about 20:1 are often discussed in prerenal patterns, but the result is nonspecific.
BUN/creatinine ratio = BUN ÷ serum creatinine. Ratios above about 20:1 are often discussed in prerenal patterns, but the result is nonspecific.
Review status
Source-mapped educational formula
Source-mapped educational formula
Limitations
Educational estimate only; not a diagnosis, prescription, or treatment plan.
Educational estimate only; not a diagnosis, prescription, or treatment plan.
Formula and method
BUN/creatinine ratio = BUN in mg/dL ÷ serum creatinine in mg/dL.
Medical safety note: This page is for education only and should not replace professional medical advice. For emergencies, medication decisions, or severe symptoms, contact a qualified clinician or local emergency service.
Limitations and when not to rely on this result
- Educational estimate only; not a diagnosis, prescription, or treatment plan.
- Result depends on accurate inputs and may not apply to complex medical situations.
- Use clinician judgment, local guidance, and urgent care pathways when symptoms are severe.
Frequently asked questions
How is BUN/creatinine ratio calculated? +
Divide BUN by serum creatinine when both are in mg/dL.
What does a high ratio mean? +
A high ratio can be seen with prerenal patterns, dehydration, GI bleeding, high protein intake, catabolic states, or steroid use.
Can this diagnose kidney failure? +
No. Kidney assessment requires trends, urine output, creatinine changes, urinalysis, medications, and clinical context.
What if creatinine is very low? +
Low creatinine from low muscle mass can make the ratio look high. Interpret carefully.
Is this useful with eGFR? +
It can complement eGFR and clinical assessment, but it does not replace them.