Proteinuria is a medical term used to describe high levels of protein in the urine. Under normal conditions, people do not have protein in their urine because structures in the kidneys known as glomeruli filter out proteins so that they can be reused by the body. In people with proteinuria, the protein indicates that there is a medical problem which needs to be addressed.

The cause of proteinuria is kidney damage which interferes with the function of the glomeruli, so that they cannot filter out protein. Glomerulonephritis, in which these structures become inflamed, is a common cause. Proteinuria is also associated with cardiovascular problems, including high blood pressure, and diabetes, all of which can put strain on the kidneys so that they cannot function normally. Protein in the urine can also be caused by infections and inflammations of the urinary tract.

Some people with proteinuria develop edema, especially in their hands and feet. The swelling of the hands and feet may be uncomfortable, and it can mean that shoes and rings will not fit as they normally would. Foamy urine, caused by a change in surface tension, can also develop in people with high levels of protein in their urine. Other individuals develop no symptoms, only discovering the problem during a medical exam.