Protein in urine — known as proteinuria (pro-tee-NU-ree-uh) — is any excess amount of protein found in a urine sample. Protein is one of the substances identified during urinalysis, a test to analyze the content of your urine.
Low levels of protein in urine are normal. Temporarily high levels of protein in urine aren't unusual either, particularly in younger people after exercise or during an illness. If a urinalysis shows you have protein in your urine, you might have a follow-up test that determines how much protein is present and whether it's a cause for concern.
If you have diabetes, your doctor may check for small amounts of protein in urine — also known as microalbuminuria (my-kroh-al-byoo-min-U-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.
Your kidneys filter waste products from your blood while retaining components your body needs — including proteins. However, some diseases and conditions can 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:
- Cold exposure
- Emotional stress
- Heat exposure
- Strenuous exercise
Diseases and conditions that can cause persistently elevated levels of protein in urine, which may indicate kidney disease, include:
- Amyloidosis (buildup of abnormal proteins in your organs)
- Certain drugs
- Chronic kidney disease
- Glomerulonephritis (inflammation in the kidney cells that filter waste from the blood)
- Goodpasture's syndrome (disease involving the kidneys and lungs)
- Heart disease
- Heart failure
- High blood pressure (hypertension)
- Hodgkin's lymphoma (Hodgkin's disease)
- IgA nephropathy (Berger's disease) (kidney inflammation resulting from a buildup of the antibody immunoglobulin A)
- Kidney infection
- Multiple myeloma
- Orthostatic proteinuria (urine protein level rises when in an upright position)
- Pericarditis (inflammation of the sac that surrounds the heart)
- Rheumatoid arthritis
- Sarcoidosis (development and growth of clumps of inflammatory cells in your organs)
- Urinary tract infection (UTI)
When to see a doctor
If urinalysis or another urine test has revealed protein in your urine, ask your doctor whether you need further testing. Protein in urine can be temporary, so your doctor may recommend a repeat test first thing in the morning or a few days later.
Your doctor may order other tests, such as a 24-hour urine collection, to determine if there is a cause for concern.