Proteinuria is the presence of too much protein in the urine. It is typically a sign of kidney disease, often in people diagnosed with diabetes, but also can occur with pregnancy, lupus, and other health conditions.12 One of the main signs of proteinuria is foamy urine, but that can occur in healthy people, too.
Proteinuria often has no symptoms and some studies find that only about a third of cases are linked to kidney disease.3 In many cases, the underlying cause is never known or the accurate diagnosis relies on other co-occurring symptoms.
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Symptoms
Typically, there is very little protein in your urine. The kidneys provide a filtration barrier that prevents most proteins from leaving the blood, and those that do make it through are simply reabsorbed back into circulation.
Different mechanisms can permit protein to escape into the urine, including even transient proteinuria due to dehydration, or due to postural proteinuria. The latter condition, sometimes called nutcracker syndrome, occurs when when blood vessels are compressed and affects both adults and children.4
Foamy urine is not diagnostic of proteinuria. In fact, some people may have bilirubinuria (excess bilirubin in the urine) or retrograde ejaculation (the backflow of semen into the bladder).3
If the kidneys have sustained only mild damage, proteinuria may be minimal to moderate, depending upon where in the kidney the damage has occurred.
Foamy Urine as a Sign of Proteinuria
While foamy or frothy urine can be a sign of proteinuria, other factors can cause urine to be foamy on occasion. The foaminess should be persistent over time before considering other causes, like decreased kidney function.3
Nephrotic Syndrome
If the loss of kidney function is severe, proteinuria may be a part of a more serious condition called nephrotic syndrome. This causes fluid buildup and dyslipidemia (unhealthy levels of cholesterol or fats).5
Symptoms of nephrotic syndrome include:6
- Foamy urine
- Swelling of the hands and feet
- Puffiness around the eyes, particularly in the morning
- The buildup of fluids in the abdomen, despite loss of appetite
- Shortness of breath
- Fatigue or tiredness

Causes of Proteinuria
Kidney disease is usually the first condition a healthcare provider will explore when there is excess protein in the urine. But other conditions can cause proteinuria, some of which occur independently of kidney disease.
Kidney Disease
Proteinuria is a common feature of kidney disease. It is typically caused by damage to the tiny clusters of blood vessels that act as filters in the kidneys, called glomeruli. When these filters are damaged, more protein can escape into the urine.7
There are many causes of this, and it is collectively referred to as glomerular disease.8
Proteinuria can also be caused by damage to tiny structures called proximal tubules that return protein to the bloodstream. When these units are damaged, protein is forced into the urine. The impaired function affects other organs too, especially the heart.9
Proteinuria is common with the two main types of kidney disease:
- Acute kidney injury (AKI): This is the sudden decline in kidney function due to dehydration, low blood pressure, shock, congestive heart failure (the heart cannot pump enough blood for the body's needs), blood or fluid loss, and other causes.10
- Chronic kidney disease (CKD): This is the progressive loss of kidney function, mainly due to high blood pressure, diabetes, glomerular disease, and polycystic kidney disease (a genetic disease that causes clusters of cysts in the kidneys).7
Other conditions that affect the kidney can lead to proteinuria and include:11
- Fanconi's syndrome: A genetic disorder that can damage proximal tubules12
- Goodpasture syndrome: An autoimmune disease affecting the lungs and kidneys
- Granulomatosis with polyangiitis: An autoimmune disease that causes the inflammation of blood vessels throughout the body
- Lupus: An autoimmune disease that affects multiple organs
- Preeclampsia: A pregnancy complication characterized by high blood pressure13
- Renal cell carcinoma: The most common type of kidney cancer.14 Some cancer therapies also may contribute to proteinuria.15
Overflow Proteinuria
Overflow proteinuria occurs when the amount of low molecular weight proteins in the blood exceeds the amount the kidneys can filter. When this happens, the excess protein exits the body in urine.16
Certain conditions can cause overproduction of proteins that, in turn, leads to overflow proteinuria:
- Multiple myeloma: A rare type of blood cancer that can lead to an excessive accumulation of proteins called light chains17
- Rhabdomyolysis: The abnormal breakdown of muscle tissues that can lead to the buildup of proteins called myoglobulins18
Medications
There are certain medications that can cause proteinuria. These drugs are classified as nephrotoxic because they are toxic to the kidneys.19
Medications and substances commonly associated with nephrotoxicity include:19
- Nonsteroidal anti-inflammatory drugs (NSAIDs): Used to reduce inflammation and pain
- Alcohol: Drinking can harm the kidneys as well as liver
- Illicit drugs: Street drugs such as methamphetamine
- Antibiotics: Used to treat bacterial infections
- Contrast dye: Dyes used for imaging procedures, like computed tomography (CT) scans
- Laxatives: Prescription products used for bowel prep and procedures
- Chemotherapy drugs: Used to treat cancer15
- Rifampin: Drug used to treat tuberculosis20
How to Treat Proteinuria
Proteinuria is not a disease but rather a condition caused by another illness. As such, the treatment is mainly focused on resolving or managing the underlying cause.
For instance, the symptoms of acute kidney injury—formerly known as acute kidney failure—will usually clear once the underlying condition is treated. In most cases, the kidney function will return to normal with no permanent damage to the kidneys.10
With chronic kidney disease (CKD), the focus is placed on improving the function of the kidneys to slow the progression of the disease, often linked to diabetes and high blood pressure.21 With respect to proteinuria:
- Lifestyle measures (such as diet, exercise, and weight loss) will help to control diabetes and high blood pressure as ways to slow progression of the disease.
- Medications like ACE inhibitors and angiotensin II receptor blockers help reduce urine protein levels.22
- Statin drugs, used to reduce cholesterol, appear to have similar benefits in people with CKD.23
Are There Tests to Diagnose the Cause of Proteinuria?
Diagnosing proteinuria can be diagnosed with a simple urine test.24 This involves dipping a specially treated paper strip into a sample of urine. Results are returned within one to two minutes.
To measure the exact amount of protein excreted in the urine, your healthcare provider may recommend a 24-hour urine collection test. By evaluating the composition of urine collected over 24 hours (including different types of proteins and waste products), the lab can calculate how much protein is passed each day.
Urine dipstick tests are commonly performed in a healthcare provider's office, but there are at-home and mail-in tests that you can use in the privacy of your own home. However, the urine dipstick test may not be as accurate. Talk with your healthcare provider about the urine test.
Levels of Protein in Urine
Normal results of a urine test called the urine albumin-creatinine ratio (uACR) fall below 30 milligrams per gram. For levels between 30 and 299 mg, it's considered moderately high and increases your risk (or a diagnosis, in some cases) of kidney disease. At 300 mg or more, the likelihood of kidney disease is much higher.24
While these tests can tell you whether or not you have proteinuria, they cannot tell you what caused it if you do. For this, you would need to see a healthcare provider. Other tests may include:25
- Blood tests: The comprehensive metabolic panel includes kidney function tests and glucose. This checks how well your kidneys are filtering blood a waste product called creatinine. Also, glucose is determined and followed up for uncontrolled diabetes, if appropriate. A hemoglobin A1c test also checks for glucose control.
- Urinalysis: This is a urine test that can measure levels of a type of protein called albumin, characteristically seen in people with proteinuria. It can also check for signs of infection (based on the presence of white blood cells) or evidence of bleeding.
- Blood pressure: This checks to see if you have low blood pressure.
- Toxicology test: This can check blood or urine for the presence of nephrotoxic substances, including illicit drugs.
- Special imaging tests: These could include ultrasound (uses sound waves), computed tomography (CT) (creates three-dimensional X-ray images), or magnetic resonance imaging (MRI) (uses magnetic and radio waves).
- Kidney biopsy: This involves the insertion of a long, hollow needle through the wall of the abdomen to obtain a sample of kidney tissue. The anatomic pathologist can then evaluate the sample to check for signs of infection, necrosis (tissue death), cancer, or other abnormalities.
When to See a Healthcare Provider
Proteinuria doesn't always mean there's a serious problem, but seek immediate medical care if you experience the following:26
- Gradually diminishing urine output
- Swelling of the legs, ankles, or feet
- Extreme tiredness or weakness
- Shortness of breath
- Nausea or vomiting
- Chest pain or pressure
- Irregular heartbeat
These are common signs of kidney failure, a condition in which the kidney function has dropped so severely that you may require hospitalization to avoid illness or death.26 This is especially true if the symptoms develop over the span of several hours or days. Without treatment, kidney failure is associated with a high risk of death.
Summary
Proteinuria is the presence of excess presence of protein in the urine. It commonly occurs in people with kidney disease when the filters of the kidneys, called the glomeruli, are damaged.
There are other causes as well, including drugs that are toxic to the kidneys and medical conditions that cause the excess production of protein in the body. The treatment of proteinuria varies by the underlying cause. If chronic kidney disease is involved, exercise, changes in diet, weight loss, and medications may help slow the progression of the disease and help alleviate proteinuria.