BUN is blood urea nitrogen. Creatinine is a natural product of basic muscle breakdown. The kidney filters these and releases it in the urine. So they help to measure kidney function
It is useful to check if kidneys are functioning properly, diagnose acute or chronic renal disease such as congestive heart failure, the onset of UTI, gastrointestinal bleeding, etc.
A sample of blood is collected from the elbow pit for BUN. No preparation is required prior to the test. And creatinine can be measured by a urine test. And the ratio is calculated
The normal levels depend on muscle mass and age. In general it is, 0.5 to 1.2 milligrams per deciliter (mg/dL).The normal BUN is 7 to 20 mg/dL. And the normal ratio is between 10 to 1 and 20 to 1.