The 24-hour urine protein test checks how much protein is being spilled into the urine, which can help detect disease or other problems. Urine samples are collected in one or more containers over a period of 24 hours. The containers are kept in a cool environment and then sent to a lab for analysis. Specialists then check the urine for protein. When higher-than-normal amounts of protein are in the urine, it’s called proteinuria. This is often a sign of kidney damage and disease.