Protein in the urine contains very small amounts of protein, and the 24-hour urine protein quantification is often less than 20 mg. Protein in human blood is not filtered through the kidneys, and the glomerulus has a negatively charged basement membrane, and there are filter pores composed of dendritic cells, and the pore size of protein is larger than the filter pores composed of dendritic cells, and protein also has a negative charge and the same charge as the basement membrane, so the principle of homopolar repulsion arises. Therefore, most of the protein will be absorbed into the body. A small amount of protein with small molecular weight is filtered through the glomerulus, and about 95% is reabsorbed into the body by the renal tubules, while only a small amount of protein is excreted through the urine. When kidney disease occurs, such as glomerular disease, or tubular damage, protein can be leaked from the kidneys into the urine, and routine urine tests can reveal large amounts of proteinuria.