Proteinuria refers to excess protein in the urine. While some amount of protein in the urine is normal, excessive amounts of protein in the urine are a sign that the kidneys are not working properly due to a number of different reasons. The main protein in the blood is albumin, and this is also the main protein in urine. For this reason, proteinuria is sometimes referred to as albuminuria. Diabetes and hypertension (high blood pressure) are two chronic conditions that can cause kidney damage over time, leading to excess protein in the urine. Acute (sudden onset) problems with the kidneys, like acute renal failure, also cause proteinuria. Some conditions can transiently increase the amount of protein in the urine, including emotional stress, vigorous exercise, fever, or exposure to heat or cold extreme temperatures.