What is proteinuria or protein in the urine?

Proteinuria is the medical term for protein in the urine. Normally, urine contains only small amounts of protein—so when higher levels are found, it may be a sign that the kidneys are not working properly.

Proteins like albumin belong in the blood, not in the urine. In healthy kidneys, tiny filters called glomeruli prevent large molecules like protein from leaking into the urine. If these filters are damaged—due to high blood pressure, diabetes, inflammation, or kidney disease—protein can slip through and end up in the urine.

Proteinuria is often one of the earliest signs of kidney damage, even when you feel completely fine. That is why routine urine tests are important, especially for people at higher risk of kidney problems.

Doctors usually detect protein in the urine using a urine dipstick test or a urine albumin-to-creatinine ratio (ACR). The ACR test compares the amount of albumin (a type of protein) to creatinine in your urine. A higher-than-normal ratio may suggest early kidney issues and prompt further testing.

In some cases, proteinuria may be temporary. Exercise, fever, dehydration, or stress can cause short-term protein in the urine. But if it persists, it needs to be evaluated.

You may not notice symptoms early on. As protein levels increase, you might see foamy urine, swelling in the legs or around the eyes, or signs of fluid retention. These symptoms are caused by the body losing too much protein, which helps hold fluid in the blood vessels.

Treating proteinuria usually involves managing the underlying condition, such as controlling blood pressure, treating diabetes, or reducing inflammation. In many cases, medication and lifestyle changes can help reduce protein leakage and protect the kidneys from further damage.

Detecting proteinuria early is one of the best ways to catch kidney problems before they become serious.

Looking for more questions?

Visit our Kidney Questions page for all other topics explained in plain language.