Also Known As
Microalbumin
ACR
UACR
Formal Name
Urine Albumin; Albumin-to-Creatinine Ratio
This article was last reviewed on
This article waslast modified on July 1, 2018.
At a Glance
Why Get Tested?

To detect early kidney disease in those with diabetes or other risk factors, such as high blood pressure (hypertension)

When To Get Tested?

Annually after a diagnosis of type 2 diabetes; annually 5 years after diagnosis of type 1 diabetes

Sample Required?

A random, timed, overnight, or 24-hour urine sample

Test Preparation Needed?

None

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Albumin is a major protein normally present in blood. The urine albumin test detects and measures the amount of albumin in the urine. The presence of a small amount of albumin in the urine may be an early indicator of kidney disease. A small amount of albumin in the urine is sometimes referred to as urine microalbumin or microalbuminuria. "Microalbuminuria" is slowly being replaced with the term "albuminuria," which refers to any elevation of albumin in the urine.

Plasma, the liquid portion of blood, contains many different proteins, including albumin. One of the many functions of the kidneys is to conserve plasma proteins so that they are not released along with waste products when urine is produced. There are two mechanisms that normally prevent protein from passing into urine: (1) the glomeruli provide a barrier that keeps most large plasma proteins inside the blood vessels and (2) the smaller proteins that do get through are almost entirely reabsorbed by the tubules.

Protein in the urine (proteinuria) most often occurs when either the glomeruli or tubules in the kidney are damaged. Inflammation and/or scarring of the glomeruli can allow increasing amounts of protein to leak into the urine. Damage to the tubules can prevent protein from being reabsorbed.

Albumin is a plasma protein that is present in high concentrations in the blood, and when the kidneys are functioning properly, virtually no albumin is present in the urine. If a person's kidneys become damaged or diseased, however, they begin to lose their ability to conserve albumin and other proteins. This is frequently seen in chronic diseases, such as diabetes and hypertension, with increasing amounts of protein in the urine reflecting increasing kidney dysfunction.

Albumin is one of the first proteins to be detected in the urine with kidney damage. People who have consistently detectable small amounts of albumin in their urine (albuminuria) have an increased risk of developing progressive kidney failure and cardiovascular disease in the future.

A urine albumin test is used to screen for kidney disease in people with chronic conditions such as diabetes and high blood pressure. It can detect small amounts of albumin that escape from the blood through the kidneys into the urine several years before significant kidney damage becomes apparent. Most of the time, tests for albumin and creatinine are done on a urine sample collected randomly (not timed) and an albumin-to-creatinine ratio is calculated. This is done to provide a more accurate indication of the how much albumin is being released into the urine. (For more, see "The Test" tab.)

How is the sample collected for testing?

random sample of urine, a timed urine sample (such as 4 hours or overnight), or a complete 24-hour urine sample is collected in a clean container. The health practitioner or laboratory will provide a container and instructions for properly collecting the sample that is needed.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

Accordion Title
Common Questions
  • How is it used?

    The urine albumin test or albumin/creatinine ratio (ACR) is used to screen people with chronic conditions, such as diabetes and high blood pressure (hypertension) that put them at an increased risk of developing kidney disease. Studies have shown that identifying individuals in the very early stages of kidney disease helps people and healthcare providers adjust treatment. Controlling diabetes and hypertension by maintaining tight glycemic control and reducing blood pressure delay or prevent the progression of kidney disease.

    Albumin is a protein that is present in high concentrations in the blood. Virtually no albumin is present in the urine when the kidneys are functioning properly. However, albumin may be detected in the urine even in the early stages of kidney disease. (See the "What is being tested?" section for more.)

    If albumin is detected in a urine sample collected at random, over 4 hours, or overnight, the test may be repeated and/or confirmed with urine that is collected over a 24-hour period (24-hour urine).

    Most of the time, both albumin and creatinine are measured in a random urine sample and an albumin/creatinine ratio (ACR) is calculated. This may be done to more accurately determine how much albumin is escaping from the kidneys into the urine. The concentration (or dilution) of urine varies throughout the day with more or less liquid being released in addition to the body's waste products. Thus, the concentration of albumin in the urine may also vary.

    Creatinine, a byproduct of muscle metabolism, is normally released into the urine at a constant rate and its level in the urine is an indication of the urine concentration. This property of creatinine allows its measurement to be used to correct for urine concentration in a random urine sample. The American Diabetes Association has stated a preference for the ACR for screening for albuminuria indicating early kidney disease. Since the amount of albumin in the urine can vary considerably, an elevated ACR should be repeated twice within 3 to 6 months to confirm the diagnosis.

  • When is it ordered?

    According to the American Diabetes Association and National Kidney Foundation, everyone with type 1 diabetes should get tested annually, starting 5 years after onset of the disease, and all those with type 2 diabetes should get tested annually, starting at the time of diagnosis. If albumin in the urine (albuminuria) is detected, it should be confirmed by retesting twice within a 3-6 month period. People with hypertension may be tested at regular intervals, with the frequency determined by their healthcare provider.

  • What does the test result mean?

    Moderately increased albumin levels found in both initial and repeat urine tests indicate that a person is likely to have early kidney disease. Very high levels are an indication that kidney disease is present in a more severe form. Undetectable levels are an indication that kidney function is normal.

    The presence of blood in the urine, a urinary tract infection, vigorous exercise, and other acute illnesses may cause a positive test result that is not related to kidney disease. Testing should be repeated after these conditions have resolved.

  • Is there anything else I should know?

    Studies have shown that elevated levels of urinary albumin in people with diabetes or hypertension are associated with increased risk of developing cardiovascular disease (CVD). More recently, research has been focused on trying to determine if increased levels of albumin in the urine are also indicative of CVD risk in those who do not have diabetes or high blood pressure.

  • What is the difference between serum/plasma albumin, prealbumin, and urine albumin tests?

    Although the names are similar, albumin and prealbumin are completely different molecules. They are both proteins made by the liver, however, and both have been used historically to evaluate nutritional status. Serum/plasma (or blood) albumin is now more often used to screen for and help diagnose liver or kidney disease and is tested on a blood sample. The urine albumin test (also called a microalbumin test) detects and measures albumin in the urine as an early indicator of kidney damage.

  • Is there anything I can do to prevent microalbuminuria?

    Yes, if you are diabetic, follow your healthcare provider's instructions for maintaining tight control over your blood glucose level. Keeping high blood pressure under control is also effective in preventing kidney damage that leads to microalbuminuria. Some studies have shown that those who have albuminuria can prevent it from worsening or may reverse it with good glycemic and blood pressure control, or by quitting smoking.

  • Are there other reasons for having increased urine albumin levels?

    Yes, albuminuria is not specific for diabetes. It may also be associated with hypertension (high blood pressure), some lipid abnormalities, and several immune disorders. Elevated results may also be caused by vigorous exercise, blood in the urine, urinary tract infection, dehydration, and some drugs.

View Sources

Sources Used in Current Review

Reviewer May 2015: Bridgit O. Crews, PhD, DABCC, Scientific Director, Northern California Kaiser Regional Laboratories.

National Kidney Foundation. KDOQITM Clinical Practice Guidelines and Clincal Practice Recommendations for Diabetes and Chronic Kidney Disease. Am J Kidney Dis 49:S1-S180, 2007 (suppl 2).

American Diabetes Association. Standards of Medical Care in Diabetes—2015. Diabetes Care 38:S1-S94, 2015 (suppl 1).

Mancia G, Fagard R, Narkiewicz K, et al. 2013 ESH/ESC guidelines for the management of arterial hypertension: the Task Force for the Management of Arterial Hypertension of the European Society of Hypertension (ESH) and of the European Society of Cardiology (ESC). Eur Heart J 28:2159-219 (2013).

Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney inter., Suppl. 2013; 3: 1-150.

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Greg Miller, Ph.D. Professor of Pathology. Director of Clinical Chemistry. Director of Pathology Information Systems. Virginia Commonwealth University.

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