Blood Urea Nitrogen (BUN) Unit Converter

Blood urea nitrogen (BUN) measures the amount of urea nitrogen in your blood. Urea is a waste product created when your liver breaks down proteins from food or from your own tissues.

When proteins are metabolized, they release nitrogen in the form of ammonia. Because ammonia is toxic, your liver converts it into urea, which is then filtered out by your kidneys and excreted in urine.

BUN is commonly used as a marker of kidney function, though it is also influenced by protein intake, hydration status, and liver function.

Urea is produced in the liver through the urea cycle, which converts toxic ammonia (a byproduct of protein breakdown) into urea. The kidneys then filter urea from the blood and excrete it in urine.