About BUN
BUN (Blood Urea Nitrogen) measures the concentration of urea — a protein breakdown product — in your blood, which healthy kidneys continuously filter out and excrete in urine. Elevated BUN can point to kidney dysfunction, dehydration, high protein intake, or gastrointestinal bleeding; low BUN can indicate malnutrition or liver disease. The BUN-to-creatinine ratio is clinically useful: a high ratio suggests dehydration or bleeding, while a low ratio with elevated BUN points to intrinsic kidney disease.