Healthy kidneys remove extra fluid and waste from your blood, but let proteins and other important nutrients pass through and return to your blood stream. When your kidneys are not working as well as they should, they can let some protein (albumin) escape through their filters, into your urine. When you have protein in your urine, it is called proteinuria (or albuminuria). Having protein in your urine can be a sign of nephrotic syndrome, or an early sign of kidney disease. When your kidneys are first starting to have problems, and you do not have a lot of protein in your urine, you will not notice any symptoms. The only way to know if you have protein in your urine is to have a urine test. The test for protein in the urine measures the amount of albumin in your urine, compared to the amount of creatinine in your urine. This is called the urine albumin-to-creatinine ratio (UACR). A UACR more than 30 mg/g can be a sign of kidney disease.