Protein in urine — also called proteinuria (pro-tee-NU-ree-uh) — is an excess of bloodborne proteins in urine. Protein is one of the substances measured in a lab test to analyze the contents of urine (urinalysis).
The term "proteinuria" is sometimes used interchangeably with the term "albuminuria," but these terms have somewhat different meanings. Albumin (al-BYOO-min) is the most common type of protein circulating in blood. Some urine tests only detect an excess of albumin in urine. Excess albumin in urine is called albuminuria (al-BYOO-mih-NU-ree-uh). Proteinuria refers to an excess of multiple blood proteins in urine.
Low levels of protein in urine are typical. Temporarily high levels of protein in urine aren't unusual either, particularly in younger people after exercise or during an illness.
Persistently high levels of protein in urine may be a sign of kidney disease.
Your kidneys filter waste products from your blood while keeping what your body needs — including proteins. However, some diseases and conditions allow proteins to pass through the filters of your kidneys, causing protein in urine.
Conditions that can cause a temporary rise in the levels of protein in urine, but don't necessarily indicate kidney damage, include:
Tests to identify protein in urine are critical for diagnosing and screening for diseases of the kidneys or other conditions affecting kidney function. These tests are also used to monitor disease progression and treatment effect. These diseases and conditions include:
Other conditions and factors affecting the kidneys that may result in protein in urine include:
If a urine test reveals protein in your urine, your health care provider may ask you to have more testing done. Because protein in urine can be temporary, you may need to repeat a urine test first thing in the morning or a few days later. You also may need to do a 24-hour urine collection for lab testing.
If you have diabetes, your doctor may check for small amounts of protein in urine — also known as microalbuminuria (my-kroh-al-BYOO-mih-NU-ree-uh) — once or twice each year. Newly developing or increasing amounts of protein in your urine may be the earliest sign of diabetic kidney damage.