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  • Also Known As:
  • Sed Rate
  • Sedimentation Rate
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Test Quick Guide

About the Test

The erythrocyte sedimentation rate, also known as ESR, is based on how quickly red blood cells (RBCs) settle inside a test tube.
An ESR test is used to assess inflammation in the body. Many conditions can cause an abnormal ESR, so an ESR test is typically used with other tests to diagnose and monitor different diseases.

Purpose of the test

The main purpose of an ESR test is to detect abnormal levels of inflammation in the body. Measuring ESR is primarily used for diagnosis and monitoring of different health conditions:

  • Diagnosis is the process of finding the cause of a patient’s symptoms. Because many health problems can cause an ESR test to be abnormal, the test alone cannot diagnose conditions. However, when combined with other tests, an ESR test may help detect infections, autoimmune diseases, blood disorders, kidney disease, and many other health problems.
  • Monitoring is the process of periodically assessing a patient’s health after a diagnosis. An ESR test may be used periodically to see how inflammatory health conditions change over time. It can also help assess a patient’s response to treatments for certain disorders.

Any individual patient should talk with their health care provider for more details about the specific purpose of ESR testing in their situation.

What does the test measure?

An ESR test measures how fast red blood cells (RBCs), also known as erythrocytes, fall to the bottom of a test tube. The falling of these cells is called sedimentation, which is measured in millimeters per hour (mm/h).

When should I get an erythrocyte sedimentation test?

An ESR test may be appropriate if you have unexplained symptoms like a fever, muscle or joint pain, or other problems without a clear cause. In these situations, an ESR is usually combined with other tests, such as a complete blood count, comprehensive metabolic panel, and arthritis tests, to evaluate your overall health and look for signs of specific health problems.

Your doctor may also recommend an ESR test to help track your health if you have previously been diagnosed or received treatment for infections, autoimmune diseases, or other inflammatory health conditions.

Finding an Erythrocyte Sedimentation Rate Test

How to get tested

An ESR test requires a blood sample and is typically conducted at a doctors office, urgent care facility, or hospital and has to be ordered by a health care provider. The person conducting the test will either be a phlebotomist who is trained to draw blood or another health care professional.

Can I take the test at home?

An ESR test cannot be conducted at home. It has to be done by a trained medical professional in a medical setting where the blood can be quickly analyzed after it has been drawn.

How much does the test cost? 

The price of an ESR test varies based on where you have the test done and whether you have health insurance. The cost of the test may increase if you have other tests performed along with an ESR.

If you want to know more about the cost of the procedure and how much your insurance covers, you should contact your insurance company. If you do not have any kind of health insurance coverage, you can ask the testing facility about any available financial assistance programs for the uninsured.

Taking an Erythrocyte Sedimentation Test

The ESR test is performed with a sample of blood that is drawn from a vein in your arm. The blood draw process is typically carried out in a medical office, lab testing site, or hospital.

Before the test

There is no special test preparation required for an ESR test. Before the test, make sure to tell your doctor about any drugs or supplements that you take because some medications may affect your results.

During the test

The blood draw for an ESR test usually only takes a few minutes to perform.

The health professional taking your blood sample will start by using an alcohol wipe to clean a small area of your skin near a vein. A needle will then be inserted into the vein, and blood will be drawn into an attached tube. Once enough blood has been drawn, the needle is removed.

There may be some pain, such as a pinch or sting, when the needle pierces the skin and is removed from your arm.

After the test

Most people do not have any negative reactions to an ESR test, but you may have some bruising or tenderness around the puncture site. There are no activity restrictions after the test, but you should contact your doctor if you notice any signs of infection such as redness, swelling, or persistent pain.

Erythrocyte Sedimentation Rate Test Results

Receiving test results

An ESR test is usually performed within a couple of hours after your blood is drawn, and the RBCs in the test tube are monitored for one hour to determine the ESR.

Once the results are available, you may receive a test report by mail or electronically. Your doctor may also contact you to discuss your ESR test results.

If multiple tests are being performed along with the ESR test, your doctor may wait for all the results to be available before discussing the results with you. This allows them to interpret the test results together.

Interpreting test results

The erythrocyte sedimentation rate is reported in millimeters per hour (mm/h) and reflects how quickly the red blood cells in your sample fall toward the bottom of a test tube.

There is no universal definition of a normal erythrocyte sedimentation rate. Age, sex, and other factors can influence ESR, so there is no reference range for this test that applies to all people.

Instead, the results of testing are interpreted based on an individual’s situation. This includes considering their symptoms and the results of any other tests that have been performed.

If an ESR is abnormally high, it means that the red blood cells fell faster than expected. This usually happens when the RBCs have more protein within them, which causes them to stick together.

Many conditions can cause an ESR to become elevated. Most often, an elevated ESR is related to conditions that cause inflammation, but it can also be caused by other health problems. Examples of conditions that can cause an abnormally high ESR include:

  • Infections
  • Autoimmune conditions like lupus and rheumatoid arthritis
  • Anemia
  • Kidney or thyroid disease
  • Some types of cancer
  • Tissue injury or trauma

It is also possible for the ESR to be very low or much lower than expected. This may be caused by conditions such as:

  • Red blood cell disorders
  • Heart failure
  • Some liver and kidney problems

It is important to remember that an ESR test alone cannot diagnose any disease or medical condition. It must be used in conjunction with other tests to detect and monitor health problems. An ESR test should always be interpreted by a doctor who can explain its significance.

Are test results accurate?

While an ESR test is considered to be dependable for assessing inflammation, it is not a perfect test.

It is possible for healthy people to have an abnormal ESR and for people with health problems to have normal ESR test results. In addition, certain specific factors may affect test accuracy, including:

  • Age: ESR can change significantly with age, and doctors may have to adjust for a patient’s age to determine if their ESR is normal.
  • Sex: ESR may be affected by biological sex. Males typically have a lower ESR.
  • Menstruation and pregnancy: Both menstruation and pregnancy can influence ESR.
  • Body weight: A normal ESR level for any individual may change based on whether or not they have obesity.
  • Alcohol consumption: Drinking alcohol may cause an ESR test result to be lower than expected.
  • Medications: Some types of medications may have an effect on an ESR test.

Do I need follow-up tests?

Because an ESR test by itself cannot diagnose any health conditions, additional testing is common if the test results are abnormal. Other tests to assess inflammation, such as a C-reactive protein (CRP) test, are frequently conducted with the ESR test.

Other types of follow-up tests may be prescribed based on the ESR test results, your symptoms, your overall health, and the results of other tests that may have already been conducted.

Questions for your doctor about erythrocyte sedimentation test results

When going over your test results with the doctor, the following questions can be helpful:

  • Did the test detect any abnormalities?
  • If so, what kind of abnormal result was detected?
  • What is the most likely explanation for my test result?
  • What other tests were conducted along with the ESR?
  • Do I need any follow-up testing?

View Sources

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A.D.A.M. Medical Encyclopedia. ESR. Updated May 6, 2019. Accessed November 2, 2021. https://medlineplus.gov/ency/article/003638.htm

Centers for Disease Control and Prevention. Multisystem inflammatory syndrome. Updated May 20, 2021. Accessed November 2, 2021. https://www.cdc.gov/mis/mis-c/hcp/

Frank, R. Peripheral venous access in adults. In: Wolfson, ed. UpToDate. Updated November 5, 2021. Accessed December 15, 2021. https://www.uptodate.com/contents/peripheral-venous-access-in-adults

Giavarina D, Capuzzo S, Pizzolato U, Soffiati G. Length of erythrocyte sedimentation rate (ESR) adjusted for the hematocrit: Reference values for the TEST 1 method. Clin Lab. 2006;52(5-6):241-5. PMID: 16812950.

Kushner I. Acute phase reactants. In: Furst D, ed. UpToDate. Updated July 30, 2021. Accessed November 7, 2021. https://www.uptodate.com/contents/acute-phase-reactants

Kushner I. Lab interpretation: High erythrocyte sedimentation rate in adults. In: Shmerling R, ed. UpToDate. Updated March 30, 2020. Accessed November 2, 2021. https://www.uptodate.com/contents/high-erythrocyte-sedimentation-rate-in-adults

MedlinePlus: National Library of Medicine. C-reactive protein (CRP) test. Updated December 3, 2020. Accessed November 16, 2021. https://medlineplus.gov/lab-tests/c-reactive-protein-crp-test/

MedlinePlus: National Library of Medicine. How to prepare for a lab test. Updated March 8, 2021. Accessed November 4, 2021. https://medlineplus.gov/lab-tests/how-to-prepare-for-a-lab-test/

MedlinePlus: National Library of Medicine. Erythrocyte sedimentation rate. Updated July 31, 2021. Accessed November 2, 2021. https://medlineplus.gov/lab-tests/erythrocyte-sedimentation-rate-esr/

Tishkowski K, Gupta V. Erythrocyte sedimentation rate. In: StatPearls. Updated May 9, 2021. Accessed November 2, 2021. https://www.ncbi.nlm.nih.gov/books/NBK557485/

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