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Erythrocyte Sedimentation Rate

Does this test have other names?

ESR, sed rate

What is this test?

Erythrocyte sedimentation rate (ESR) is a blood test that measures how quickly erythrocytes, or red blood cells, separate from a blood sample that has been treated so the blood will not clot. During this test, a small amount of your blood will be placed in an upright tube and a laboratory specialist will measure the rate at which your red blood cells settle toward the bottom of the tube after one hour.

If you have a condition that causes inflammation or cell damage, your red blood cells tend to clump together, which makes them heavier, so they settle faster. The faster your red blood cells settle and fall, the higher your ESR. A high ESR tells your doctor that you may have an active disease process in your body. 

Why do I need this test?

You may need this blood test if you have symptoms of one of the diseases that may cause ESR to go up.

You may also need this test if you have already been diagnosed with a disease that causes a high ESR. The test can allow your doctor to see how well you are responding to treatment.

The ESR blood test is most useful for diagnosing or monitoring diseases that cause pain and swelling due to inflammation. Other symptoms may include fever and weight loss. These diseases include:

  • Temporal arteritis

  • Rheumatoid arthritis

  • Polymyalgia rheumatica

ESR is not used as a screening test in people who do not have symptoms or a diagnosis of disease because many conditions can cause it to increase. It might also go up in many normal situations. ESR doesn't tell your doctor whether you have a specific disease. It only suggests that you may have an active disease process in your body. 

What other tests might I have along with this test?

You may have other diagnostic tests if your doctor is doing this test to diagnose a disease.

Your doctor may do an ESR alone if he or she is monitoring a disease you already have.

Because ESR tells your doctor only what is happening right now, you may need to have the test repeated over time. 

What do my test results mean?

A result for a lab test may be affected by many things, including the method the laboratory uses to do the test. If your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

ESR is measured in millimeters per hour (mm/h). The normal values are:

  • 0 to 10 mm/h in children

  • 0 to 15 mm/h in men younger than 50

  • 0 to 20 mm/h in men older than 50

  • 0 to 20 mm/h in women younger than 50

  • 0 to 30 mm/h in women older than 50

ESR above 100 mm/h is most likely caused by an active disease.

If your ESR is high, it can mean many things, for instance, you may have:

Disease that causes inflammation in your body

  • Active infection

  • Cancer

  • Heart disease

  • Kidney disease

  • Blood disease

  • Another disease 

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore. 

What might affect my test results?

Many factors that are not active diseases can increase your ESR. These include:

  • Pregnancy

  • Old age

  • Being female

  • Having a menstrual period

  • Having recently eaten a fatty meal

  • Being obese

  • Taking certain drugs

How do I get ready for this test?

You don't need to prepare for this test. Be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use. Tell your doctor if you ate a fatty meal recently, if you are having your period, or if you may be pregnant.