The sedimentation rate (sed rate) blood
test measures how quickly red blood cells (erythrocytes) settle in a test
The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Results are usually available right away.
millimeters per hour (mm/hr)
High sedimentation rates may be caused
Low values may be caused by:
What Affects the Test
Reasons you may not be able to
have the test or why the results may not be helpful include:
- Having your menstrual
- Age. Sed rates normally increase with
- Medicines. Many medicines can change the results of this test.
Be sure to tell your doctor about all the nonprescription and prescription
medicines you take.
What To Think About
- Even though some problems, such as giant cell
arteritis, almost always cause a high sedimentation rate (sed rate), the test
cannot be used by itself to identify a specific disease. Results of a sed rate
test are considered along with your symptoms, other test results, and medical
- Some diseases that cause inflammation do not increase
the sed rate, so a normal sed rate does not always rule out a disease.
- Some doctors use the C-reactive protein (CRP) blood test instead
of the sed rate test to help identify inflammatory conditions. For more
information, see the topic
C-Reactive Protein (CRP).
Other Works Consulted
Fischbach FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.
Primary Medical Reviewer
||Kathleen Romito, MD - Family Medicine
Specialist Medical Reviewer
||E. Gregory Thompson, MD - Internal Medicine
||June 11, 2010