Erythrocyte Sedimentation Rate (ESR)

Erythrocytes are red blood cells. When blood is placed in a tube, red blood cells (erythrocytes) gradually settle to the bottom. This is called Erythrocyte Sedimentation Rate (ESR). Inflammation can cause Erythrocytes to clump. Because these clumps are denser than individual cells, they settle to the bottom more quickly.

What is an Erythrocyte Sedimentation Rate (ESR) test used for?

An Erythrocyte Sedimentation Rate (ESR) test is a blood test that can show if you have inflammation in your body.

Inflammation is your immune system’s response to injury, infection, and many types of conditions.  Types of conditions include, for example, immune system disorders, certain cancers, blood disorders, arthritis, vasculitis, and inflammatory bowel disease.

Why do you need an ESR?

Your health care provider may order an ESR if you have symptoms of a condition that causes inflammation.  Your symptoms will depend on the condition you may have.

What do the test results mean?

Your provider will use the results of your ESR test along with your medical history, symptoms, and other test results to make a diagnosis.  An ESR test alone cannot diagnose conditions that cause inflammation.

A high ESR test result may be from a condition that causes inflammation.

A low ESR test result means your red blood cells sank more slowly than normal.  Blood disorders, heart failure, certain kidney and liver problems may result in a low ESR test result.

If your ESR results are not normal, it doesn’t always mean you have a medical condition that needs treatment.  Pregnancy, a menstrual cycle, aging, obesity, drinking alcohol regularly, and exercise can affect ESR results.  Certain medicines and supplements may also affect your results, so be sure to tell your provider about any medicines or supplements you are taking.

It’s possible to have a condition that causes inflammation and still have a normal ESR result.  A C-reactive protein (CRP) test is often done with an ESR to provide more information.