Erythrocyte Sedimentation Rate

Does this test have other names?

ESR, sed rate

What is this test?

Erythrocyte sedimentation rate (ESR) is a blood test. It 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 put in an upright tube. A lab specialist will measure the rate that your red blood cells settle toward the bottom of the tube after 1 hour.

If you have a condition that causes inflammation or cell damage, your red blood cells tend to clump together. This 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 you need this test?

You may need this 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 keeping track of diseases that cause pain and swelling from 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 to diagnose disease because many conditions can cause it to increase. It might also go up in many normal cases. 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 you have along with this test?

You may have other tests if your doctor is doing this test to diagnose a disease. One of these tests is called a C-reactive protein test, or CRP. This test also measures active inflammation in the body.

Your doctor may do an ESR alone if they are keeping track of 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 your test results mean?

Test results may vary depending on your age, sex, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your doctor what your test results mean for you.

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

• 0 to 15 mm/hr in men

• 0 to 20 mm/hr in women

ESR above 100 mm/h is most likely caused by an active disease. For instance, you may have:

• A disease that causes inflammation in your body.

• An active infection.

• Cancer.

• Heart disease.

• Kidney disease.

• Blood disease.

• Diabetes.

• Collagen vascular disease.

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand.

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore.

What might affect your test results?

Many things 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 medicines.

How do you 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 illegal 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.