Protein in Urine: What It Means, Causes, and How the Test Is Done

A line reading "protein" or "traces of protein" has appeared on the urine test report. This is not a diagnosis. We explain what proteinuria means, where the numbers come from, and how to properly collect a urine sample for testing.

What protein in urine and proteinuria are

Proteinuria is the detection of protein in a urine test. Normally there is very little protein in urine. The kidneys filter excess water and waste from the blood. Proteins are large molecules: they give the body energy, repair muscles, and help immunity. Tiny kidney filters do not let them out. If the filters are damaged, protein leaks into the urine.

A high level of protein in urine over a long period can be the first sign of kidney disease or another condition that has damaged the kidney filters. Protein in a urine test is a working result, like any other, and there is nothing to be ashamed of.

When protein in urine requires a doctor's attention

In the early stages of kidney disease there are usually no symptoms: the problem is found through a blood or urine test done for another reason. Later, fatigue, swelling of the feet, ankles, and hands, puffy eyelids, shortness of breath, nausea and vomiting, blood in the urine, foamy urine, dry skin, itching, numbness, loss of appetite and weight, muscle cramps, sleep problems, difficulty thinking clearly, and urinating more or less often than usual appear.

People go to the doctor if protein persists in repeat tests and if such symptoms are present. Diabetes, high blood pressure, heart disease, and a family history of kidney disease are a separate reason: with these, the doctor may recommend regular check-ups.

Proteinuria itself is not a reason to call an ambulance. 103/112 — for signs of stroke, heart attack, or another life-threatening condition.

Traces of protein in urine: what they mean

Physiological proteinuria in a single sample is up to 0.033 g/L, and daily excretion is 30–50 milligrams per day. Protein from the urinary tract and prostate does not exceed 150 milligrams per day; such a small concentration is not detected in single samples.

A short-term increase is caused by heavy exercise, dehydration, food, stress, fever, cold, and pregnancy. A false-positive test can occur with sulfonamides, penicillins, butamide, chlorhexidine, and X-ray contrast agents, and in women — when the urine is contaminated with vaginal discharge. If protein remains high in repeat samples, it is more often a matter of kidney disease or kidney damage from other conditions. The amount of protein is associated with the extent of damage, and the cause is determined through further testing.

Why protein appears in urine in women and adults

Non-pathological forms are postural (orthostatic), febrile, and exercise proteinuria. Pathological forms are glomerular: glomerulonephritis, tumors, drug-induced disease, and nephrotic syndrome. The kidneys are damaged by diabetes, high blood pressure, high cholesterol, kidney infections, recurrent stones, an enlarged prostate, and long-term use of lithium and nonsteroidal anti-inflammatory drugs.

During pregnancy, normal is up to 30 milligrams of protein, 30–300 milligrams is microalbuminuria, and from 300 milligrams is macroalbuminuria; a level above 300 milligrams per day is often associated with preeclampsia.

Protein in a child's urine

Children also have little protein in their urine. Daily excretion up to one month is 240 milligrams per square meter, and after one month — 60 milligrams per square meter per day. Febrile and postural proteinuria in children are considered non-pathological. Hereditary tubular forms include cystinosis, Wilson–Konovalov disease, Lowe syndrome, and galactosemia. If protein is repeatedly found in a child's tests, the doctor determines the cause.

How a urine protein test is performed and how to collect a sample

The methods vary: qualitative (Heller's test, with sulfosalicylic acid, with boiling), semi-quantitative (Brandberg–Roberts–Stolnikov method, test strips), and quantitative (turbidimetric, colorimetric). A protein test is often part of a general urine test, and a 24-hour collection gives a fuller picture.

No preparation is needed. A single sample is collected using the clean midstream method:

• wash your hands with soap and dry them;
• open the container without touching the inside;
• wipe the genital area with a wipe: the entire glans of the penis, after retracting the foreskin; in women, spread the labia and wipe from front to back;
• urinate for a couple of seconds into the toilet, then into the container, without touching it to the body;
• collect the required volume up to the mark, close it, and return the container.

Tell the staff in advance about menstruation and bleeding hemorrhoids. The test causes no harm. Home test strips are sold without a prescription, but the result is interpreted by a doctor.

The material is for reference: the report is a reason to talk to a doctor, not a substitute for a consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer