Share this page:
Also known as: Sed rate; Sedimentation rate; Westergren sedimentation rate
Formal name: Erythrocyte Sedimentation Rate

At a Glance

Why Get Tested?

To determine the presence of one or more types of conditions, including infections, tumors, inflammation, and those leading to the breakdown or decreased function of tissue or organs (degenerative), and/or to monitor the progress of disease or effect of therapy

When to Get Tested?

When your doctor thinks that you might have a condition (see above) and to monitor the course of temporal arteritis, polymyalgia rheumatica, or rheumatoid arthritis

Sample Required?

A blood sample drawn from a vein in the arm

Test Preparation Needed?


The Test Sample

What is being tested?

Erythrocyte sedimentation rate (ESR) is an indirect measure of the degree of inflammation present in the body. It actually measures the rate of fall (sedimentation) of erythrocytes (red blood cells) in a sample of blood that has been placed into a tall, thin, vertical tube. Results are reported in millimeters of clear plasma that are present at the top portion of the tube after one hour.

Normally, red cells fall slowly, leaving little clear plasma. Increased blood levels of abnormal proteins or certain other proteins called acute phase reactants such as fibrinogen or immunoglobulins, which are increased in inflammation, cause the red blood cells to fall more rapidly, increasing the ESR. Acute phase reactants and the ESR may be increased in a number of different conditions, such as infections, autoimmune diseases, and cancer.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

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

No test preparation is needed.

The Test

Common Questions

Ask a Laboratory Scientist

This form enables you to ask specific questions about your tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. If your questions are not related to your lab tests, please submit them via our Contact Us form. Thank you.

* indicates a required field

Please indicate whether you are a   

You must provide a valid email address in order to receive a response.

| Read The Disclaimer

Spam Prevention Equation

| |

Article Sources

« Return to Related Pages

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson R, Pincus M, eds. Philadelphia, PA: Saunders Elsevier: 2007, 465-466.

Pagana K, Pagana T. Mosby's Manual of Diagnostic and Laboratory Tests. 3rd Edition, St. Louis: Mosby Elsevier; 2006, 233-235.

Cha CH, et al (Aug 24, 2009). Erythrocyte Sedimentation Rate Measurements by TEST 1 Better Reflect Inflammation Than Do Those by the Westergren Method in Patients With Malignancy, Autoimmune Disease, or Infection. American Journal of Clinical Pathology. 2009;131(2):189-194. Available online at through Accessed April 2010.

(May 7, 2009) Medline Plus Medical Encyclopedia: ESR. Available online at Accessed April 2010.

Sources Used in Previous Reviews

Brigden, M (October 1, 1999). Clinical Utility of the Erythrocyte Sedimentation Rate. American Family Physician: American Academy of Family Physicians. Available online at through

Shojania, Kam (2000). Rheumatology: 2. What laboratory tests are needed? Canadian Medical Association Journal: CMAJ 2000, 162(8):1157-63. Available online at through

MEDLINEplus (October 3, 2001). Medical Encyclopedia: ESR. U.S. National Library of Medicine, Bethesda, MD. MEDLINEplus. Available online at

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

Pagana, Kathleen D. & Pagana, Timothy J. (1999). Mosby's Diagnostic and Laboratory Test Reference 4th Edition: Mosby, Inc., Saint Louis, MO.

Zlonis M: The mystique of the erythrocyte sedimentation rate - a reappraisal of one of the oldest laboratory tests still in use. Clin Lab Med 1993;13:787-800.