Proteinuria refers to an excess of proteins, such as albumin, in the urine. It can be caused by damage to the glomeruli or renal tubules in the kidneys that prevents the normal reabsorption of proteins from the urine. People at highest risk include those with diabetes, hypertension, obesity, or a family history of kidney disease. Tests like the urine albumin-to-creatinine ratio can detect proteinuria. Treatment focuses on controlling blood pressure and blood sugar through medications like ACE inhibitors that protect the kidneys from further damage.