Erythrocyte Sedimentation Rate (ESR)
Reviewed
An erythrocyte sedimentation rate (ESR) is a blood test that can show if you have inflammation in your body. It measures how quickly your red blood cells settle at the bottom of a test tube; faster settling may indicate inflammation.
Preparation and collection
You don't need any special preparations for this test. However, if your provider ordered other tests on your blood sample, you may need to fast (not eat or drink) for several hours before the test. Your provider will let you know if there are any special instructions.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- An ESR test alone cannot diagnose which condition is causing inflammation.
- It is possible to have a condition that causes inflammation and still have a normal ESR result.
- Normal ESR levels vary based on age and sex.
- Factors like pregnancy, menstrual cycle, aging, obesity, regular alcohol consumption, exercise, and certain medicines or supplements can affect ESR results.
- The test does not provide a specific diagnosis; it is a nonspecific marker of inflammation.
What to do next
If your ESR results are not normal, it does not always mean you have a medical condition that needs treatment. Your provider will use your ESR results along with your medical history, symptoms, and other tests (such as a C-reactive protein test) to make a diagnosis and determine the next steps. Discuss all results and concerns with your healthcare provider.
Evidence source
U.S. National Library of Medicine: Erythrocyte Sedimentation Rate (ESR)