The Urea Nitrogen Urine (UNU) test measures the amount of urea, a waste product from protein breakdown, that your kidneys are excreting. This test is the essential partner to the Blood Urea Nitrogen (BUN) test. By comparing your blood and urine levels, your doctor can get a highly accurate picture of your body's protein balance and overall kidney function. This test, often a 24-hour collection, provides a complete, dynamic picture of your metabolic and kidney function.