Urine Albumin (Microalbumin) and Albumin to Creatinine Ratio (ACR)

Also Known As

Microalbumin

ACR

UACR

Albumin (urine)

Albumin-to-Creatinine Ratio

This article was last reviewed on

October 6, 2018.

This article waslast modified on September 19, 2019.

At a Glance

Why Get Tested?

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

When To Get Tested?

Once a diagnosis of type 2 diabetes is made and then annually; 5 years after diagnosis of type 1 diabetes and then annually; at regular intervals when you have high blood pressure

Sample Required?

A 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. Your healthcare practitioner or laboratory will provide a container and instructions for properly collecting the sample that is needed.

Test Preparation Needed?

None

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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, but 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. The urine albumin test (formerly called microalbumin) detects and measures the amount of albumin in the urine to screen for kidney disease.

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 (ACR) is calculated. This is done to provide a more accurate indication of the how much albumin is being released into the urine. 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 when measuring albumin in a random urine sample.

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:

Specialized structures in the kidney called glomeruli are composed of loops of specialized capillaries that filter the blood, allowing small substances to pass through towards the urine, but provide a barrier that keeps most large plasma proteins inside the blood vessels.
The smaller proteins that do get through are almost entirely reabsorbed by tubes (tubules) that have a number of sections that collect the fluid and molecules that pass through the glomeruli.

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.

If a person's kidneys become damaged or diseased, 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.

Common Questions

How is the test used?

A urine albumin test and albumin to creatinine ratio (ACR) are used to screen for kidney disease in people with chronic conditions, such as diabetes and high blood pressure (hypertension). 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. 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.

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).

For urine samples collected randomly (not timed), both albumin and creatinine usually are measured and an albumin to creatinine ratio (ACR) is calculated. This is done to provide a more accurate indication of the how much albumin is being released into the urine. 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 starting 5 years after onset of the disease and then annually, and all those with type 2 diabetes should get tested starting at the time of diagnosis and then annually. 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 practitioner.
What does the test result mean?

If albumin in undetectable in the urine, it is an indication that kidney function is normal.

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.

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 I can do to prevent albuminuria (microalbuminuria)?

Yes, if you have diabetes, follow your healthcare practitioner's instructions for maintaining control over your blood glucose level. Keeping high blood pressure under control is also effective in preventing kidney damage that leads to albumin in urine (albuminuria). Some studies have shown that those who have albuminuria can prevent it from worsening or may reverse it with good glycemic control and blood pressure control, or by quitting smoking.
Are there other reasons for having increased urine albumin levels?

Yes, albumin in the urine (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.
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 or plasma (or blood) albumin is now more often used to screen for and help diagnose liver or kidney disease. The urine albumin test detects and measures albumin in the urine as an early indicator of kidney damage.
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. There is currently some evidence that albuminuria is associated with an increased risk of death in adults.

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Health Professionals – LOINC

LOINC Observation Identifiers Names and Codes (LOINC®) is the international standard for identifying health measurements, observations, and documents. It provides a common language to unambiguously identify things you can measure or observe that enables the exchange and aggregation of clinical results for care delivery, outcomes management, and research. Learn More.

Listed in the table below are the LOINC with links to the LOINC detail pages.

LOINC	LOINC Display Name
44292-1	Albumin/Creatinine DL <= 20 mg/L (12H U) [Mass ratio]
13705-9	Albumin/Creatinine (24H U) [Mass ratio]
14958-3	Albumin/Creatinine DL <= 20 mg/L (24H U) [Mass ratio]
9318-7	Albumin/Creatinine (U) [Mass ratio]
14959-1	Albumin/Creatinine DL <= 20 mg/L (U) [Mass ratio]
20621-9	Albumin/Creatinine Test strip Ql (U)
76401-9	Albumin/Creatinine (24H U) [Ratio]
77254-1	Albumin/Creatinine DL <= 1.0 mg/L (24H U) [Ratio]
59159-4	Albumin/Creatinine DL <= 20 mg/L (24H U) [Ratio]
32294-1	Albumin/Creatinine (U) [Ratio]
77253-3	Albumin/Creatinine DL <= 1.0 mg/L (U) [Ratio]
30001-2	Albumin/Creatinine Test strip detection limit <= 20 mg/L (U) [Ratio]
89998-9	Albumin/Creatinine DL <= 3.0 mg/L (U) [Ratio]
30000-4	Albumin/Creatinine DL <= 20 mg/L (U) [Ratio]
14585-4	Albumin/Creatinine (U) [Molar ratio]
57369-1	Albumin DL <= 20 mg/L (12H U) [Mass/Vol]
21059-1	Albumin (24H U) [Mass/Vol]
53530-2	Albumin DL <= 1.0 mg/L (24H U) [Mass/Vol]
30003-8	Albumin DL <= 20 mg/L (24H U) [Mass/Vol]
43605-5	Albumin DL <= 20 mg/L (4 hour U) [Mass/Vol]
1754-1	Albumin (U) [Mass/Vol]
53531-0	Albumin DL <= 1.0 mg/L (U) [Mass/Vol]
11218-5	Albumin Test strip detection limit <= 20 mg/L (U) [Mass/Vol]
89999-7	Albumin DL <= 3.0 mg/L (U) [Mass/Vol]
14957-5	Albumin DL <= 20 mg/L (U) [Mass/Vol]
43607-1	Albumin DL <= 20 mg/L (12H U) [Mass/Time]
63474-1	Albumin DL <= 20 mg/L (18H U) [Mass/Time]
1755-8	Albumin (24H U) [Mass/Time]
53532-8	Albumin DL <= 1.0 mg/L (24H U) [Mass/Time]
90000-1	Albumin DL <= 3.0 mg/L (24H U) [Mass/Time]
14956-7	Albumin DL <= 20 mg/L (24H U) [Mass/Time]
43606-3	Albumin DL <= 20 mg/L (4 hour U) [Mass/Time]
56553-1	Albumin DL <= 20 mg/L (8H U) [Mass/Time]
49002-9	Albumin Unsp time (U) [Mass/Time]
49023-5	Albumin Unsp time DL <= 20 mg/L (U) [Mass/Time]
1753-3	Albumin Ql (U)
50949-7	Albumin Test strip Ql (U)
77158-4	Albumin DL <= 3.0 mg/L (U) [Moles/Vol]

View Sources

Sources Used in Current Review

2018 Review completed by Adetoun A Ejilemele, MB.ChB., DABCC, Clinical Chemist, KP Regional Laboratory.

Ritte R, Luke J, Nelson C, Brown A, O'Dea K, Jenkins A, Best JD, McDermott R, Daniel M, Rowley K. Clinical outcomes associated with albuminuria in central Australia: a cohort study. BMC Nephrol. 2016 Aug 5;17(1):113. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4974695/. Accessed 10/2/2018.

Chong J, Fotheringham J, Tomson C, Ellam T.. doi: 10.1093/ndt/gfy242. Renal albumin excretion in healthy young adults and its association with mortality risk in the US population. Nephrol Dial Transplant. 2018 Aug 6.

American Diabetes Association. (2018) Standards of medical Care in Diabetes. Diabetes Care 2018 Jan; 41 (Supplement 1): S105-S118. Available online at https://doi.org/10.2337/dc18-S010. Accessed 10/2/2018.

Rovin BH. Assessment of urine protein excretion and evaluation of isolated non-nephrotic proteinuria in adults. Available online through https://www.uptodate.com. Accessed 10/2/2018.

Tietz Textbook of Clinical chemistry and Molecular Diagnosis 6th Edition. Rifai N, Horvath AR, Wittwer CT, eds. St Louis: Elsevier.

Sources Used in Previous Reviews

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.

Corbett, JV. Laboratory Tests & Diagnostic Procedures with Nursing Diagnoses, 4th ed. Stamford, Conn.: Appleton & Lang, 1996. Pp. 73-74.

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

Nuovo, J. (1999 June). Albumin-to-Creatinine Ratio for Detection of Microalbuminuria. American Family Physician, Tips from other Journals [On-line journal]. Available online at http://www.aafp.org/afp/990600ap/tips.html#31.

Fitz, M. (1999 February 2). Spot Urine Albumin to Creatinine Ratio. Loyola University Chicago Stritch School of Medicine. [On-line information, Medicine 1]. Available online at http://www.meddean.luc.edu/Lumen/meded/MEDICINE/medclerk/renal13.htm.

Ehrmeyer, S. (2003 January). Using a creatinine ratio in urinalysis to improve the reliability of protein and albumin results. Medical Laboratory Observer, Features 35 (1) [On-line journal]. Available online at http://www.mlo-online.com/articles/mlo0103cliniss.htm.

Loghman-Adham, M. (1998 October 1). Evaluating Proteinuria in Children. American Family Physician [On-line journal]. Available online at http://www.aafp.org/afp/981001ap/loghman.html.

Virtual Hospital: University of Iowa Family Practice Handbook, 3rd Edition: Hematologic, Electrolyte, and Metabolic Disorders: Bibliography. Available online at http://www.vh.org/Providers/ClinRef/FPHandbook/Chapter05/Bibliography05.html

ARUP Laboratory Guidebook. Available online at http://www.arpulab.com/guides/clt/.

American Diabetes Association: Community and Resources. Available online at http://www.diabetes.org.

National Kidney Foundation. Fact Sheet: Microalbuminuria In Diabetic Kidney Disease. Available online at http://www.kidney.org/news/newsroom/fs_new/microalbindbkd.cfm. Accessed December 2008.

MedlinePlus Medical Encyclopedia. Microalbuminuria test. Available online at http://www.nlm.nih.gov/MEDLINEPLUS/ency/article/003591.htm. Accessed December 2008.

US FDA. Diabetes Information, Glucose Meters & Diabetes Management. Available online at http://www.fda.gov/Diabetes/glucose.html#22. Accessed December 2008.

American Diabetes Association. Clinical Practice Recommendations 2008. Diabetes Care. January 2008, Volume 31, Supplement 1. Available online at http://care.diabetesjournals.org/content/vol31/Supplement_1/. Accessed December 2008.

Wang TJ, Gona P, Larson G, et al. Multiple biomarkers for the prediction of first major cardiovascular events and death. New England Journal of Medicine. 21 Dec 2006. 355;25:2631-2639.

High Levels Of Urinary Albumin In The Normal Range Predict Hypertension. ScienceDaily (June 25, 2008). Available online at http://www.sciencedaily.com/releases/2008/06/080625123002.htm. Accessed December 2008.

Holly Kramer et al. Urine Albumin Excretion and Subclinical Cardiovascular Disease. Hypertension. 2005;46:38. Available online at http://hyper.ahajournals.org/cgi/content/abstract/46/1/38. Accessed December 2008.

Lin, J. (Updated 2012 February 21) Microalbumin. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/2088184-overview#showall. Accessed April 2012.

Khardori, R. (Updated 2012 April 4) Type 2 Diabetes Mellitus. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/117853-overview. Accessed April 2012.

Mayo Clinic Staff (Updated 2010 July 31). Microalbumin test. Mayo Clinic [On-line information]. Available online at http://www.mayoclinic.com/print/microalbumin/MY00143/METHOD=print&DSECTION=all. Accessed April 2012.

Durani, Y. (Reviewed 2012 March). Urine Test: Microalbumin-to-Creatinine Ratio. Nemours [On-line information]. Available online at http://kidshealth.org/parent/system/medical/test_mtc_ratio.html. Accessed April 2012.

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

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