Test Details: 24 hours Urine urea is a quantitative urine test done on urine sample collected over 24 hours. It's a measure of protein breakdown in the body within 24 hours. Urea excreted also reflects kidney function in the body. This test is mainly used to determine necessary protein intake in severely ill patients. High level of Urea can also be observed in hyperthyroidism. Low levels are seen in patients with malnutrition or liver disease etc. Levels also vary with age (lower levels in children and pregnant women).