Sed Rate (Erythrocyte Sedimentation Rate or ESR) Test

A simple blood test to help detect inflammation, the sed rate test is a valuable diagnostic tool.


What is a sed rate (erythrocyte sedimentation rate or ESR) test?

Sed rate (erythrocyte sedimentation rate, also known as ESR) is a simple blood test that helps detect inflammation in the body. The test measures the rate of fall (sedimentation) of red blood cells (erythrocytes) in a sample of blood placed in a tall vertical tube. Increased sed rate indicates inflammation.

Sed rate tests are also used to monitor the progress of an inflammatory disease.

Inflammation may be linked to a number of conditions including infections, some cancers, and autoimmune diseases.

A sed rate test is done through blood taken by needle from a vein in your arm.


Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Why is a sed rate (erythrocyte sedimentation rate or ESR) test done?

A sed rate test may be done when your doctor suspects you have a condition causing inflammation. Sed rate is called a nonspecific test because it does not diagnose specific illnesses but adds to the information about the presence and levels of inflammation.

A sed rate may be ordered to help in diagnosing and monitoring conditions including:

Test Details

How does the sed rate (erythrocyte sedimentation rate or ESR) test work?

The blood is placed into a tall thin tube and the test measures the rate of fall (sedimentation) of erythrocytes (red blood cells). The red cells settle faster than normally if there is alteration of blood proteins, which indicates inflammation.

The results are the measurement, in millimeters, of the clear fluid (plasma) left at the top of the tube after a period of 1 hour.


Additional Details

How do I prepare for a sed rate (erythrocyte sedimentation rate or ESR) test?

A sed rate test is a simple blood draw from your arm. Unless your doctor gives you other instructions, there is nothing you need to do to prepare.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 03/14/2018.

Learn more about our editorial process.

Appointments 216.444.2606