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Erythrocyte Sedimentation Rate

(ESR; Sed Rate)

Pronounced: Eh-RITH-ro-site sed-i-ment-ay-shun

What Is an Erythrocyte?

Erythrocyte is another name for red blood cell. The test for erythrocyte sedimentation rate (ESR) measures how fast red blood cells settle to the bottom of a test tube.

Reason for the Test

An ESR test is done to find out whether someone has a disease associated with infection and inflammation. This test is not specific enough to point out the cause or location of problems. Changes in ESR measurements are more informative than a single test. For example, an ESR that is getting lower may be a sign that treatment is working.

This test may also be done to help a doctor decide between 2 possible diagnoses. For example, ESR can help tell 2 different diseases apart, such as rheumatoid arthritis, in which ESR is elevated, from osteoarthritis, in which ESR is not elevated.

Type of Sample Taken

A blood sample is taken from a vein in the arm.

Prior to Collecting the Sample

Certain drugs and health problems can affect the result of the ESR test. Discuss your health and lifestyle choices with your doctor before taking the test.

During the Sample Collection

You will be asked to sit. An area on your arm will be cleaned with a wipe. A large band will be tied around your arm. The needle will be put in a vein. A tube will collect the blood from the needle. The band on your arm will be taken off. After the blood is collected, the needle will be removed. Gauze will be held on the site to help stop bleeding. You may also be given a bandage. This test takes about 5 to 10 minutes.

After Collecting the Sample

After the blood sample is taken, you may need to stay seated for 10 to 15 minutes. If you are lightheaded, you may need to stay seated longer. When you feel better, you can leave.

A bit of blood may ooze from the vein beneath the skin. It will cause a bruise. A bruise will usually fade in a day or two.

Call your doctor right away if you have redness, swelling, lasting bleeding, or pain.


It will take several hours to days to get your test results. It depends on whether repeat tests are needed to see a pattern over time.

One test is not likely to help diagnose a health problem or find out whether treatment is working. Your doctor will probably do a series of these tests to find out if the rate stays high or decreases.

An increase in ESR may be due to:

Diseases or health problems that may have no increase in ESR are:

Diseases or health problems with a decrease in ESR are:

Talk to your doctor about your test results. A test may point to an illness that you do not have. It can also miss an illness that you may have. The doctor will check your symptoms and all test results before making a diagnosis.


Erythrocyte sedimentation rate. Davis's Comprehensive Handbook of Laboratory & Diagnostic Tests with Nursing Implications, 6th ed; 2015:751-757. EBSCO Nursing Reference Center Plus. Available at:https://www.ebscohost.com/nursing/products/nursing-reference-center. Accessed August 1, 2019.

Erythrocyte sedimentation rate measurement. EBSCO DynaMed website. Available at:http://www.dynamed.com/topics/dmp~AN~T906898/Erythrocyte-sedimentation-rate-measurement. Updated October 8, 2018. Accessed August 1, 2019.

ESR. Lab Tests Online website. Available at: http://labtestsonline.org/understanding/analytes/esr/tab/test. Updated March 12, 2018. Accessed August 1, 2019.

Last reviewed June 2019 by EBSCO Medical Review Board Daniel A. Ostrovsky, MD  Last Updated: 10/23/2019