BUN stands for Blood Urea Nitrogen. It is a blood test that measures the amount of urea nitrogen in your blood. Urea nitrogen is a waste product formed when your body breaks down proteins. The liver produces ammonia from protein digestion, which contains nitrogen; this nitrogen combines with other elements to form urea. The urea travels through the bloodstream to the kidneys, which filter it out and remove it from the body through urine

. A normal BUN level typically ranges from about 6 to 20 mg/dL, though this can vary slightly depending on the laboratory

. The BUN test is primarily used to assess kidney function. High BUN levels may indicate that the kidneys are not working properly, as they are not effectively removing urea from the blood. Elevated BUN can be caused by kidney disease, dehydration, heart failure, gastrointestinal bleeding, or high protein intake, among other conditions

. Low BUN levels may be seen in liver disease, malnutrition, or overhydration

. In summary, the BUN test helps evaluate how well your kidneys are functioning by measuring the concentration of urea nitrogen in your blood, a key waste product of protein metabolism