What is BUN?
The Blood Urea Nitrogen (BUN) test measures the amount of nitrogen in your blood that comes from the waste product urea. Urea is produced in the liver when protein is broken down and is primarily cleared from the body by the kidneys.
Why Measure BUN?
A BUN test is a key indicator used to evaluate kidney function. If your kidneys are not functioning at full capacity to remove urea, your BUN levels will rise. However, levels can also be affected by dehydration, high-protein diets, or heart failure.
- High BUN: Often suggests kidney injury, disease, or dehydration.
- Low BUN: Can be seen in liver disease, overhydration, or malnutrition.
BUN to Creatinine Ratio
Clinicians often look at the ratio between BUN and Creatinine to pinpoint the cause of kidney issues. A high ratio (over 20:1) often suggests 'pre-renal' causes like low blood flow or dehydration, while a lower ratio may suggest damage to the kidney itself.
Formula:
BUN/Creatinine Ratio Formula:
Ratio = BUN (mg/dL) / Serum Creatinine (mg/dL)