Erythrocyte Sedimentation Rate (ESR)

To do an ESR test, a sample of your blood is sent to a lab. A health care professional places the sample in a tall, thin test tube and measures how quickly your red blood cells settle or sink to the bottom of the tube. Typically, red blood cells sink slowly. But inflammation makes red blood cells stick together in clumps. These clumps of cells are heavier than single cells, so they sink faster.

If an ESR test shows that your red blood cells sink faster than expected, it may mean you have a medical condition causing inflammation. How quickly the red blood cells in your sample fall to the bottom of the test tube is a sign of how much inflammation you have. Faster ESR rates mean higher levels of inflammation. But an ESR test alone cannot diagnose which condition is causing the inflammation.

Your provider will use your ESR test results, 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 means your red blood cells sank faster than normal. This may be from a condition that causes inflammation.

A low ESR test result means your red blood cells sank slower than normal. This may be caused by certain conditions as well.

If your ESR results are not normal, it doesn't always mean you have a medical condition that needs treatment. Normal ESR levels will vary, depending on your age and sex. Also, pregnancy, your 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.