Urine is a waste product from our bodies.
It is composed primarily of water (95%), urea (2%), creatinine (0.1%), uric acid (0.03%), and various minerals.
Blood flows to the kidneys and is processed by about a million filtering units called nephrons.
Each nephron comes with a funnel-like structure that removes unwanted substances from the blood.
This filtering structure is called the glomeruli, a network of tiny blood vessels that produce urine.
In healthy individuals, protein molecules in the blood should not be (or only a trace amount) able to squeeze through the glomeruli due to their big size.
However, when you have a kidney problem, especially conditions that damage the glomeruli, the filter system no longer works, and the protein may leak into urine.
One of the most common proteins found in the urine is albumin. Therefore, proteinuria is also known as albuminuria.
What is proteinuria?
Proteinuria translates as protein in the urine. However, having little protein in your urine is completely normal, and you do not have proteinuria. You have proteinuria only if your urine protein level is more than 150 mg daily.
Signs and symptoms of protein in your urine
People with mild proteinuria generally have no signs or symptoms. When the condition deteriorates, typically when the protein leakage reaches 2 to 3 g (heavy proteinuria), you may experience symptoms like:
- Urine becomes frothy or foamy (bubbles on the surface of the urine)
- Your face and eyes become puffy (facial edema), especially after waking up from bed
- Your hands and legs swell up (peripheral edema)
If your proteinuria persists, you may also suffer from the below symptoms. They should alarm you to seek medical attention.
- Dry, itchy, or numb skin
- Muscle cramps
- Extreme tiredness or fatigue
- Loss of appetite
- Weight loss
- Nausea and vomiting
- Changes in urination frequency
- Blood in the urine
- Shortness of breath
- Trouble sleeping
- Difficult concentrating and thinking clearly
How do you know if you have protein in your urine?
You may suspect yourself of having proteinuria, but there isn’t any way to tell whether your urine contains protein without medical tests.
A urine dipstick test is the most straightforward test to detect protein in the urine.
However, it doesn’t quantify the amount of protein, so your doctor will likely order another lab test called urine protein/creatinine ratio (UPCR), sometimes called urine albumin/creatinine ratio (UACR). We will look into these tests further later in this article.
Nevertheless, you may be more likely to have proteinuria if:
- You have other long-term diseases, including hypertension, diabetes mellitus, and heart failure.
- You are male. According to studies, persistent proteinuria is twice as common in males than in females.
- You are non-Hispanic Blacks and Mexican Americans. According to the US National Health and Nutrition Examination Survey, their likelihood of having proteinuria is higher.
- You are taking medication harmful to the kidneys (nephrotoxic drugs). Examples are non-steroidal anti-inflammatory drugs (NSAIDs), antihypertensive and certain antibiotics.
- You have family members with kidney or connective tissue diseases.
Should you see a doctor?
Urine in protein can be a hint for severe kidney problems. If you have already developed symptoms, you should see a doctor as soon as possible.
Some severe diseases that can come with protein in the urine, and their other symptoms are:
- Kidney failure. Symptoms include limb swelling and weight changes.
- Kidney infection (pyelonephritis). Symptoms include fever, loin pain, nausea, and painful urination.
- Kidney inflammation after the flu (post-streptococcal glomerulonephritis). Symptoms include blood in the urine, decreased need to pee, or less amount of urine, and fatigue.
- Connective tissue diseases, such as lupus, can cause kidney inflammation. Symptoms include joint pain, skin rashes, and mouth ulcers.
- Heart failure. Symptoms include shortness of breath and fatigue.
What causes protein in the urine?
We can divide all causes of protein in urine into three categories: transient (intermittent), orthostatic (related to sitting/standing or lying down), and persistent (always present).
Transient (intermittent) proteinuria is the most common type of proteinuria. It is usually benign and goes away without treatment, or when the acute condition has been resolved.
Any conditions that stress your body can make you have protein in the urine. Examples are:
- Any acute illness, especially when you have a fever
- Intense exercise or physical activity
- Emotional stress
Orthostatic proteinuria is a special type of benign proteinuria. It is not harmful, does not need treatment, and usually disappears as you age.
Studies estimated that its prevalence is around 2 to 5% among adolescents and very rare in patients above 30 years old.
Orthostatic proteinuria occurs when one leaks protein while in an upright position and spontaneously stops when lying down. The reason behind this phenomenon is yet to be discovered.
In contrast to transient and orthostatic proteinuria, persistent proteinuria almost always indicates something is not right.
Most people with persistent protein in the urine have kidney diseases, which can be primary (disease of the kidney origin) or secondary (kidney diseases induced by other prior medical conditions).
Primary kidney disease includes a damaged kidney filtering unit (glomerular disease) or tube (renal tubular disease).
Kidney abnormalities since birth, such as under-developed kidneys (renal dysplasia) and kidneys with multiple cysts (polycystic kidney disease), should be suspected when protein in the urine occurs among children and teenagers, as half of them will eventually go into kidney failure, as reported by research studies. In the elderly, kidney cancer is a potential cause of proteinuria.
In the United States, 1 in 3 diabetic people develops chronic kidney disease, according to data from the Centers for Disease Control and Prevention (CDC).
This makes diabetes the top root cause of secondary kidney disease, followed by hypertension.
Both conditions impair blood vessels in the kidneys. When this happens, kidneys can no longer work properly; thus, protein leaks into the urine.
Other diseases that can cause persistent protein in urine include connective tissue diseases, inflammation of the blood vessels (vasculitis), an abnormal buildup of protein in the kidney and other organs (amyloidosis), cancer of the blood plasma cells (myeloma), and heart failure.
Protein in the urine is relatively easy to diagnose, but finding out its root cause is another story.
When you have proteinuria, your healthcare provider will confirm the presence of protein in the urine first, followed by a series of investigations to search for the actual problem.
A urine dipstick is a screening test to confirm the presence of protein in the urine. It is simple and quick (it can be done within minutes).
The test tool is a paper strip with multiple colorful boxes. To undergo the test, you will be given a specimen cup to collect your urine. The strip will then be dipped into the urine, taken out, and compared with the color chart on the urine dipstick strip package.
The more intense the color change, the more the substance (protein, blood cells, glucose, etc.) is present in the urine.
A urine dipstick test can also be done in the lab, which provides higher accuracy and the ability to detect more substances, including identifying cells, bacteria or structures called casts.
This lab testing is called Urine Full Examination and Microscopic Examination (UFEME), or urinalysis in short.
After confirming the presence of protein in the urine, your doctor will count the exact amount of protein to interpret the severity of your condition.
The amount of protein can be quantified by either one of the below tests:
- Urine protein/creatinine ratio (UPCR) or urine albumin/creatinine ratio (UACR). Creatinine is body waste filtered by the kidneys and excreted in the urine. A normal UACR should be less than 30 mg/g. If your UACR test gives an abnormal result, your doctor might repeat the UACR tests to double-confirm.
- 24-hour urine protein. In contrast to the one-off UACR test, 24-hour urine protein is less done. You will need to collect your urine over 24 hours and send it to the lab for protein amount calculation. The normal value should be less than 100 mg/day or 10 mg/dL.
After confirming your diagnosis of proteinuria, your healthcare provider might take some of your blood to search for the underlying problem.
A kidney function test can tell you how well your kidneys are working.
One of the essential parameters measured in this test is blood urea nitrogen (BUN), which is used to calculate the estimated glomerular filtration rate (eGFR). An eGFR is the golden indicator of your kidney function.
Imaging tests such as a kidney ultrasound and computed tomography (CT) scan allow your doctor to visualize the inside of your body.
The appearance of kidneys, any mass (tumors), and other tissue abnormalities are among the features your doctor is looking for.
Sometimes, a magnetic resonance imaging (MRI) scan might be needed if surgery is indicated to treat the underlying cause of your proteinuria.
Kidney biopsy is an invasive procedure that provides the highest accuracy among all tests.
During a kidney biopsy, a thin needle is inserted through the skin at your back to remove a small piece of kidney tissue. The tissue will then be observed under a microscope to check for any injury or signs of disease.
What happens if protein in the urine is left untreated?
Untreated protein in the urine can lead to lethal consequences, including:
- Lungs congested with water (pulmonary edema) which causes breathing difficulties
- Acute kidney injury and subsequent permanent kidney damage
- Bacterial infection
- Blood clots in the arteries and veins, which stop blood flow to the blocked body part
- Cardiovascular disease, which includes heart attack, strokes, and heart failure
The goal of proteinuria treatment mainly focuses on stopping the leakage of protein, as well as treating the underlying cause.
Your doctor might prescribe you some medications, or sometimes lifestyle modification is sufficient to treat your proteinuria.
A few classes of medications that are most commonly prescribed to people with proteinuria are:
- Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor antagonists (ARB). They reduce the pressure inside your glomeruli (kidney filtering unit), slowing down the decline of kidney function and minimizing protein leakage into the urine.
- Diuretics. They are for people with more severe proteinuria, who usually have too many fluids in the body (fluid overload).
- Calcium channel blockers (CCB). Usually used together with ACE inhibitors or ARB, CCB works wonders in treating proteinuria in diabetic people.
Since most proteinuria is transient and non-serious, your doctor might suggest diet and habit modifications to speed up your recovery from having protein in the urine. These lifestyle changes include:
- Salt (sodium) restriction. A low-salt diet is proven to decrease protein excretion in the urine. A randomized control trial shows that limiting salt intake to less than 5 g daily reduces protein in the urine by 24%.
- Mild protein restriction. Although lowering protein intake reduces the amount of protein in the urine, it poses a risk of malnutrition, leading to many other serious problems. Therefore, you should consult your doctor and dietitians before changing your diet.
- Check your blood sugar and blood pressure regularly. If your proteinuria is triggered by uncontrolled diabetes or hypertension, improving your blood sugar and blood pressure control helps to stop protein leakage.
- Exercise regularly. Exercise improves your overall health, especially your cardiovascular system, which is closely linked to healthy kidneys.
- Quit smoking and tobacco use. As reported by research studies, smokers have a 2 to 3 times higher risk of having proteinuria.
- Do not self-prescribe over-the-counter medicines, especially non-steroidal anti-inflammatory drugs (NSAIDs). Examples of these drugs include aspirin (Bayer), ibuprofen (Advil), and naproxen sodium (Aleve). They can cause injury to your kidneys.
Your urine should not contain more than 150 mg (about 3% of a teaspoon) of protein daily.
When your urine protein level increases over 3.5 g in 24 hours, you have proteinuria in the “nephrotic range,” an alarming condition related to many severe kidney diseases.
Although protein in the urine is not deadly, it can hint at a more serious problem, especially when it persists or deteriorates.
It is best that you visit a doctor to find out the cause of your proteinuria soon.
Having protein in the urine does not equal having kidney disease. However, having persistent protein in the urine should warn you that something sinister is brewing, and it is a kidney problem most of the time.
Nephrotic syndrome is one of the common kidney conditions linked to massive protein in the urine. People with nephrotic syndrome pee out more than 3.5 g of protein within 24 hours.
Another closely related kidney problem is chronic kidney disease. The urine protein level (urine albumin level) is used to estimate the disease’s severity through a test called albumin-to-creatinine ratio (ACR). An ACR level greater than 300 mg/g signifies severe kidney disease.
Protein in the urine is temporary in most people and goes away once the cause has been identified and treated.
Dehydration is a common cause of transient proteinuria. Therefore, it is possible for you to have protein in the urine if you drink insufficient water, especially when you sweat a lot.
Protein in the urine is a common condition in both men and women. It is insidious- you probably are already in a more advanced stage when symptoms appear.
Therefore, be vigilant and take care of your general health. Have your regular health screening and always ask your healthcare providers if you notice any abnormalities in your body condition.