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Proteinuria

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What is proteinuria?

Proteinuria—also called albuminuria or urine albumin—is a condition in which urine contains an abnormal amount of protein. Albumin is the main protein in the blood. Proteins are the building blocks for all body parts, including muscles, bones, hair, and nails. Proteins in the blood also perform a number of important functions. They protect the body from infection, help blood clot, and keep the right amount of fluid circulating throughout the body.

As blood passes through healthy kidneys, they filter out the waste products and leave in the things the body needs, like albumin and other proteins. Most proteins are too big to pass through the kidneys' filters into the urine. However, proteins from the blood can leak into the urine when the filters of the kidney, called glomeruli, are damaged.

Proteinuria is a sign of chronic kidney disease (CKD), which can result from diabetes, high blood pressure, and diseases that cause inflammation in the kidneys. For this reason, testing for albumin in the urine is part of a routine medical assessment for everyone. Kidney disease is sometimes called renal disease. If CKD progresses, it can lead to end-stage renal disease (ESRD), when the kidneys fail completely. A person with ESRD must receive a kidney transplant or regular blood-cleansing treatments called dialysis.

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Who is at risk for proteinuria?

People with diabetes, hypertension, or certain family backgrounds are at risk for proteinuria. In the United States, diabetes is the leading cause of ESRD.1 In both type 1 and type 2 diabetes, albumin in the urine is one of the first signs of deteriorating kidney function. As kidney function declines, the amount of albumin in the urine increases.

Another risk factor for developing proteinuria is hypertension, or high blood pressure. Proteinuria in a person with high blood pressure is an indicator of declining kidney function. If the hypertension is not controlled, the person can progress to full kidney failure.

African Americans are more likely than Caucasians to have high blood pressure and to develop kidney problems from it, even when their blood pressure is only mildly elevated. In fact, African Americans are six times more likely than Caucasians to develop hypertension-related kidney failure.2

Other groups at risk for proteinuria are American Indians, Hispanics/Latinos, Pacific Islander Americans, older adults, and overweight people. These at-risk groups and people who have a family history of kidney disease should have their urine tested regularly.

1United States Renal Data System. USRDS 2007 Annual Data Report. Bethesda, MD: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, U.S. Department of Health and Human Services; 2007.

2Ibid.

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What are the signs and symptoms of proteinuria?

Proteinuria has no signs or symptoms in the early stages. Large amounts of protein in the urine may cause it to look foamy in the toilet. Also, because protein has left the body, the blood can no longer soak up enough fluid, so swelling in the hands, feet, abdomen, or face may occur. This swelling is called edema. These are signs of large protein loss and indicate that kidney disease has progressed. Laboratory testing is the only way to find out whether protein is in a person’s urine before extensive kidney damage occurs.

Several health organizations recommend regular urine checks for people at risk for CKD. A 1996 study sponsored by the National Institutes of Health determined that proteinuria is the best predictor of progressive kidney failure in people with type 2 diabetes. The American Diabetes Association recommends regular urine testing for proteinuria for people with type 1 or type 2 diabetes. The National Kidney Foundation recommends that routine checkups include testing for excess protein in the urine, especially for people in high-risk groups.

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What are the tests for proteinuria?

Until recently, an accurate protein measurement required a 24-hour urine collection. In a 24-hour collection, the patient urinates into a container, which is kept refrigerated between trips to the bathroom. The patient is instructed to begin collecting urine after the first trip to the bathroom in the morning. Every drop of urine for the rest of the day is to be collected in the container. The next morning, the patient adds the first urination after waking and the collection is complete.

Drawing of two containers for collecting urine.
Containers for a 24-hour urine collection.

In recent years, researchers have found that a single urine sample can provide the needed information. In the newer technique, the amount of albumin in the urine sample is compared with the amount of creatinine, a waste product of normal muscle breakdown. The measurement is called a urine albumin-to-creatinine ratio (UACR). A urine sample containing more than 30 milligrams of albumin for each gram of creatinine (30 mg/g) is a warning that there may be a problem. If the laboratory test exceeds 30 mg/g, another UACR test should be done 1 to 2 weeks later. If the second test also shows high levels of protein, the person has persistent proteinuria, a sign of declining kidney function, and should have additional tests to evaluate kidney function.

Drawing of a urine sample in a cup and a dipstick for testing the protein content of the urine.
Cup for a single urine sample.

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What additional tests for kidney disease may be needed?

Tests that measure the amount of creatinine in the blood will show whether a person’s kidneys are removing wastes efficiently. Having too much creatinine in the blood is a sign that a person has kidney damage. The doctor can use the creatinine measurement to estimate how efficiently the kidneys are filtering the blood. This calculation is called the estimated glomerular filtration rate, or eGFR. CKD is present when the eGFR is less than 60 milliliters per minute (mL/min).

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What should a person with proteinuria do?

If a person has diabetes, hypertension, or both, the first goal of treatment will be to control blood glucose, also called blood sugar, and blood pressure. People with diabetes should test their blood glucose often, follow a healthy eating plan, take prescribed medicines, and get the amount of exercise recommended by their doctor. A person with diabetes and high blood pressure may need a medicine from a class of drugs called angiotensin-converting enzyme (ACE) inhibitors or a similar class called angiotensin receptor blockers (ARBs). These drugs have been found to protect kidney function even more than other drugs that provide the same level of blood pressure control. Many patients with proteinuria but without hypertension may also benefit from ACE inhibitors or ARBs.

People who have high blood pressure and proteinuria, but not diabetes, also benefit from taking an ACE inhibitor or ARB. Health care providers recommend that people with kidney disease keep their blood pressure below 140/90.3 To maintain this target, a person may need to take a combination of two or more blood pressure medicines. A doctor may also prescribe a diuretic in addition to an ACE inhibitor or ARB. Diuretics are also called "water pills" because they help a person urinate and get rid of excess fluid in the body.

In addition to blood glucose and blood pressure control, the National Kidney Foundation recommends restricting dietary salt and protein. A doctor may refer a patient to a dietitian to help develop and follow a healthy eating plan.

3James PA, Oparil S, Carter BL, et al. 2014 evidence-based guideline for the management of high blood pressure in adults—report from the panel members appointed to the Eighth Joint National Committee (JNC 8). The Journal of the American Medical Association. Published online December 18, 2013.

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Points to Remember

  • Proteinuria is a condition in which urine contains a detectable amount of protein.
  • Proteinuria is a sign of chronic kidney disease (CKD).
  • Groups at risk for proteinuria include African Americans, American Indians, Hispanics/Latinos, Pacific Islander Americans, older people, overweight people, people with diabetes or hypertension, and people who have a family history of kidney disease.
  • Proteinuria may have no signs or symptoms. Laboratory testing is the only way to find out whether protein is in a person's urine.
  • Several health organizations recommend regular checks for proteinuria so kidney disease can be detected and treated before it progresses.
  • A person with diabetes, hypertension, or both should work to control blood glucose and blood pressure.

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Hope through Research

In recent years, researchers have learned much about kidney disease. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) sponsors several programs aimed at understanding kidney failure and finding treatments to stop its progression.

The NIDDK's Division of Kidney, Urologic, and Hematologic Diseases supports basic research into normal kidney function and the diseases that impair normal function at the cellular and molecular levels, including diabetes, high blood pressure, glomerulonephritis, and other diseases marked by proteinuria.

Clinical trials are research studies involving people. Clinical trials look at safe and effective new ways to prevent, detect, or treat disease. Researchers also use clinical trials to look at other aspects of care, such as improving the quality of life for people with chronic illnesses. To learn more about clinical trials, why they matter, and how to participate, visit the NIH Clinical Research Trials and You website at www.nih.gov/health/clinicaltrials. For information about current studies, visit www.ClinicalTrials.gov.

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For More Information

American Kidney Fund
11921 Rockville Pike, Suite 300
Rockville, MD 20852
Phone: 1–800–638–8299
Internet: www.kidneyfund.org leaving site icon

National Kidney Foundation
30 East 33rd Street
New York, NY 10016–5337
Phone: 1–800–622–9010 or 212–889–2210
Internet: www.kidney.org leaving site icon

Medical Education Institute, Inc.
414 D'Onofrio Drive, Suite 200
Madison, WI 53719
Phone: 1–800–468–7777 or 608–833–8033
Fax: 608–833–8366
Internet: www.meiresearch.org leaving site icon
www.lifeoptions.org leaving site icon
www.kidneyschool.org leaving site icon
www.homedialysis.org leaving site icon

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Acknowledgments

Publications produced by the Clearinghouse are carefully reviewed by both NIDDK scientists and outside experts. This publication was originally reviewed by Lee A. Hebert, M.D., Ohio State University. Jeanne Charleston, R.N., and Edgar Miller, M.D., both of the Johns Hopkins Medical Institutions, Baltimore, reviewed the updated version of the publication.

You may also find additional information about this topic by visiting MedlinePlus at www.medlineplus.gov.

This publication may contain information about medications and, when taken as prescribed, the conditions they treat. When prepared, this publication included the most current information available. For updates or for questions about any medications, contact the U.S. Food and Drug Administration toll-free at 1–888–INFO–FDA (1–888–463–6332) or visit www.fda.gov. Consult your health care provider for more information.

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National Kidney Disease Education Program

3 Kidney Information Way
Bethesda, MD 20892
Phone: 1–866–4–KIDNEY (1–866–454–3639)
TTY: 1–866–569–1162
Fax: 301–402–8182
Email: nkdep@info.niddk.nih.gov
Internet: www.nkdep.nih.gov

The National Kidney Disease Education Program (NKDEP) is an initiative of the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, U.S. Department of Health and Human Services. The NKDEP aims to raise awareness of the seriousness of kidney disease, the importance of testing those at high risk, and the availability of treatment to prevent or slow kidney disease.



National Kidney and Urologic Diseases Information Clearinghouse

3 Information Way
Bethesda, MD 20892–3580
Phone: 1–800–891–5390
TTY: 1–866–569–1162
Fax: 703–738–4929
Email: nkudic@info.niddk.nih.gov
Internet: www.kidney.niddk.nih.gov

The National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC) is a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The NIDDK is part of the National Institutes of Health of the U.S. Department of Health and Human Services. Established in 1987, the Clearinghouse provides information about diseases of the kidneys and urologic system to people with kidney and urologic disorders and to their families, health care professionals, and the public. The NKUDIC answers inquiries, develops and distributes publications, and works closely with professional and patient organizations and Government agencies to coordinate resources about kidney and urologic diseases.

This publication is not copyrighted. The Clearinghouse encourages users of this publication to duplicate and distribute as many copies as desired.


NIH Publication No. 14–4732
February 2014

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Page last updated April 2, 2014


 

The National Kidney and Urologic Diseases Information Clearinghouse is a service of the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health.

National Kidney and Urologic Diseases Information Clearinghouse
3 Information Way
Bethesda, MD 20892–3580
Phone: 1–800–891–5390
TTY: 1–866–569–1162
Fax: 703–738–4929
Email: nkudic@info.niddk.nih.gov
Internet: www.kidney.niddk.nih.gov

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