Normal urine contains very little protein, usually less than 10mg/dL, and the major serum protein that is found in normal urine is albumin.

The presence of an increased amount of protein in the urine (proteinuria) can be an indicator of renal disease. The two mechanisms which can lead to proteinuria are glomerular damage or a defect in the reabsorption process of the tubules in the nephron. The concentration of protein in the urine is not necessarily indicative of the severity of renal disease.