Proteinuria means losing of proteins through urine. Under normal conditions proteins are too big to be filtered by the glomerulus and they are practically absent in the urine (the few filtered proteins may also be resorbed in the nephron tubules). Proteinuria is an indication that a more than expected amount of proteins is passing the glomerulus suggesting glomerular disease, e.g., in diabetic nephropathy. The glomerulus also blocks the passage of blood cells and platelets (hematuria is often a sign of urinary disease although less specific of kidneys since the blood may come from the lower parts of the excretory tract).