Proteinuria: what it is, what it tells you and when it’s tested

Proteinuria is the amount of protein you lose in your urine. Healthy kidneys keep almost all protein in the blood, and very little gets into the urine. If more does, sometimes it is temporary, as after a fever or hard exercise. If it stays, the kidney filter is usually under strain.

When it’s tested

Doctors mostly order it when a urine test finds protein, to see how much there is and whether it stays. They also order it for people with kidney disease, diabetes or high blood pressure, and for people with swollen ankles or very foamy urine.

It can be measured in a full day of urine, or in a single sample, by comparing protein with creatinine. In pregnancy, urine protein is checked often.

To look for kidney damage in people who feel well, guidelines prefer urine albumin, which picks it up earlier. That is why Rosa does not test 24-hour proteinuria. Its urine test does check for protein, though, and the panel measures urine albumin.

What it tells you, and what it does not

It shows how much protein you lose. If it is a little and only once, it is often nothing. If it stays, your kidneys need checking. The more there is, the more serious the damage.

It does not say which proteins they are, or why they get through. To find out, your doctor looks at your blood, blood pressure and blood sugar, and sometimes orders other tests.

A normal proteinuria does not rule out early damage: urine albumin picks it up sooner.

That is why it is read together with other tests:

• Urinalysis: This is often where protein first shows up
• Urine albumin (microalbuminuria): It picks up kidney damage before proteinuria does
• Creatinine: It shows whether your kidneys filter well
• eGFR: The estimate of how well your kidneys filter
• Albumin: When a lot of protein is lost, blood albumin falls

Normal proteinuria levels

In a full day of urine, up to 150 mg is considered normal. Some labs use a slightly higher limit. Your report may give it in grams: 1 gram is 1000 mg.

With a single sample, the lab works out the ratio of protein to creatinine, in mg/g. The numbers to look at are similar to the 24-hour ones.

On a standard urinalysis, protein is reported as absent, trace or with plus signs. Trace protein is often harmless, but if it stays it should be measured.

What your result means

Find the row for your result, in mg per 24 hours. Which values need a doctor? Above 150, if it repeats; above 500, soon.

• Up to 150: Normal. Only a small amount of protein passes into your urine, as is normal. Nothing to do.
• Above 150, below 500: Mildly high. Often it passes: fever, exercise, too little water. If it stays, the kidneys may be under strain. Talk to your doctor: they usually repeat the test and check urine albumin.
• 500 to 3500: High. Your kidneys let a lot of protein through. Usually the kidney filter is damaged. See your doctor soon: a kidney specialist is often needed.
• 3500 or more: Very high. A very large amount of protein is lost, more than 3.5 grams a day. Legs and face often swell. See your doctor within a few days: they usually refer you to a kidney specialist.

If your proteinuria is high or at trace level

• High proteinuria: If it stays high, the kidney filter is usually under strain. Diabetes and high blood pressure are the most common causes. You need a doctor.
• Trace protein in urine: Often temporary: fever, exercise, too little water. If it repeats, your doctor measures it more precisely.

What causes proteinuria

The first are the most common and often clear up on their own. The others need looking for.

• Temporary causes: Fever, hard exercise, too little water, stress or an acute illness. They usually clear within a few days.
• Orthostatic (postural) proteinuria: In some teenagers and young adults it shows only when standing. It is harmless.
• Diabetes and high blood pressure: Over the years they damage the kidney filter. They are the most common causes of proteinuria that stays.
• Kidney diseases: Some types of inflammation of the kidney filter let a lot of protein through. A kidney specialist follows them.
• A urine infection: It can make protein appear for a few days. It is checked again after treatment.
• Blood disorders: Rarely, the bone marrow makes abnormal proteins that end up in the urine. Your doctor looks for them with specific tests.

Symptoms of proteinuria

Mild proteinuria causes no symptoms. When a lot of protein is lost, you may notice:

• Very foamy urine that does not settle
• Swollen ankles, legs or eyes, especially in the morning
• Weight gain over a few days, from retained fluid
• Tiredness

If you notice these signs, talk to your doctor. In pregnancy, talk to your gynaecologist or doctor straight away.

How to collect 24-hour urine

The lab gives you the container and the instructions. It usually goes like this:

• In the morning, pass urine in the toilet as usual and note the time: the collection starts now.
• From then on, collect all your urine in the container, day and night.
• The next morning, at the same time, pass urine into the container one last time and bring it to the lab.
• Avoid hard exercise on the day of the collection. If you have a fever, an infection or your period, it is better to wait.

What can skew the result

A few things make protein show up without a kidney problem.

• Exercise and fever: A long run or a few days of fever can raise it for a short time.
• Very concentrated urine: If you drank little, the urinalysis strip can overstate protein.
• Blood or other secretions: Period blood, semen or mucus in the sample can give a false positive.
• An incomplete collection: If some urine is missing, the 24-hour value comes out lower than the truth.

When to worry

Talk to your doctor if:

• Your proteinuria is above 150 mg per 24 hours, or protein shows up on more than one urine test.
• It is above 500: see your doctor soon, especially if there is also blood in your urine.
• It is above 3500, or your legs and face are very swollen: see your doctor within a few days.
• You are pregnant and the test finds protein: tell your gynaecologist or doctor straight away. If you also have a severe headache, problems with your vision or sudden swelling of your face and hands, call 112 or go to the emergency department.
• You pass very little or no urine for many hours, with swelling or breathlessness: call 112 or go to the emergency department.

Frequently asked questions

What are normal 24-hour urine protein levels? Up to 150 mg per 24 hours. Some labs use a slightly higher limit. The range on your own report is what counts.

Trace protein in urine: is it serious? Usually not, especially after exercise, with a fever or when you drank little. If it shows up on more than one test, your doctor measures it more precisely and checks urine albumin.

What causes proteinuria? Often it passes: fever, exercise, stress, too little water. When it stays, the most common causes are diabetes and high blood pressure. More rarely a kidney or blood disorder.

Proteinuria in pregnancy: what should I do? Tell your gynaecologist or doctor straight away. In pregnancy, urine protein is watched closely, and your gynaecologist decides what to do next.

What is the difference between proteinuria and microalbuminuria? Proteinuria measures all the protein in your urine. Microalbuminuria measures only albumin, even in small amounts. That is why it picks up kidney damage earlier.

Does Rosa test proteinuria? No, not 24-hour proteinuria. The Rosa urine test does check for protein, though, and the panel measures urine albumin, creatinine and eGFR. If your doctor wants proteinuria, they order it separately.

Sources

• Carroll and Temte, proteinuria in adults: a diagnostic approach. American Family Physician, 2000. PMID 11011862
• KDIGO clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney International, 2024. PMID 38490803
• Simerville and colleagues, urinalysis: a comprehensive review. American Family Physician, 2005. PMID 15791892