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 made when protein is broken down in your body and is normally cleared by the kidneys.
Why Measure BUN?
A BUN test is primarily used to evaluate kidney function. If your kidneys are not able to remove urea from the blood normally, your BUN level rises. Dehydration, heart failure, and high-protein diets can also affect these levels.
- High BUN: May indicate kidney injury, disease, or severe dehydration.
- Low BUN: Less common, but may be seen in liver disease or malnutrition.
BUN to Creatinine Ratio
Doctors often look at the ratio between BUN and Creatinine to determine the specific cause of kidney dysfunction. A high ratio often points toward problems 'before' the kidney, such as low blood flow or dehydration.
Formula:
Standard Ratio Formula:
Ratio = BUN (mg/dL) / Creatinine (mg/dL)