Definition

ESR stands for erythrocyte sedimentation rate. It is commonly called a “sed rate.”

It is a test that indirectly measures how much inflammation is in the body.

Alternative Names

Erythrocyte sedimentation rate; Sed rate; Sedimentation rate

How the Test is Performed

A blood sample is needed. Most of the time, blood is drawn from a vein located on the inside of the elbow or the back of the hand. The blood sample is sent to a lab.

The test measures how fast red blood cells (called erythrocytes) fall to the bottom of a tall, thin tube.

How to Prepare for the Test

There are no special steps needed to prepare for this test.

How the Test will Feel

You may feel slight pain or a sting when the needle is inserted. You may also feel some throbbing at the site after the blood is drawn.

Why the Test is Performed

Reasons why a “sed rate” may be done include:

• Unexplained fevers
• Certain types of joint pain or arthritis
• Muscle symptoms
• Other vague symptoms that cannot be explained

This test may also be used to monitor whether an illness is responding to treatment.

This test can be used to monitor inflammatory diseases or cancer. It is not used to diagnose a specific disorder.

However, the test is useful for detecting and monitoring:

• Autoimmune disorders
• Bone infections
• Certain forms of arthritis
• Inflammatory diseases