BUN/creatinine ratio
What it measures, and what changes the number.
The BUN/creatinine ratio is a calculated value, not a separate measurement. It divides the blood urea nitrogen result by the creatinine result from the same sample. Both are waste products cleared by the kidneys, and comparing them gives a different view than either number alone.
It is read alongside BUN, creatinine and eGFR, which are usually reported on the same basic or comprehensive metabolic panel, and often next to sodium and other electrolytes because hydration affects all of them.
Because it is derived from two assays, anything that shifts either input shifts the ratio. Hydration status and recent protein intake at the time of the draw can change urea more than creatinine. Labs that report urea in SI units may calculate a urea/creatinine ratio instead, which is on a different scale and cannot be compared directly. Reports may print it as BUN/CREATININE RATIO or BUN/Creat ratio.
Often read alongside: BUN (urea nitrogen), Creatinine, eGFR (CKD-EPI), Urea, Sodium