What Is an ESR Blood Test?

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Erythrocyte Sedimentation Rate (ESR) is also called Sed Rate or Sedimentation Rate. It is a simple test used to determine how much inflammation is in the body, but it cannot diagnose the specific condition causing the inflammation.

How ESR Blood Test Works

Inflammation changes the proteins in red blood cells causing them to bind to one another in clumps, making them denser than normal red blood cells. An ESR test simply notes the speed at which blood cells sink to the bottom of a test tube. The faster the blood cells fall, the more inflammation is in your body.

Primary Uses of the ESR Test

ESR tests are most often used to help diagnose rheumatoid arthritis, polymyalgia rheumatica and giant cell arteritis (GCA). Rheumatoid arthritis causes inflammation of the lining of the joints, resulting in pain, joint damage and sometimes deformity. Polymyalgia rheumatica is an inflammatory disorder causing stiffness and pain usually in the shoulders, neck, upper arms, hips and thighs; giant cell arteritis (GCA) refers to inflammation of the arterial lining and causes headaches, jaw pain and blurred vision.

Increased ESR

Increased ESR has many causes, including pregnancy, menstruation, infection or anemia. Many diseases such as kidney disease, syphilis, tuberculosis, thyroid disease and lupus also cause ESR rates to be higher than average. In addition, certain medications such as oral contraceptives, vitamin A, dextran and methyldopa (aldomet) can cause ESR readings to be higher than normal.

Very High ESR

In addition to polymyalgia rheumatica, giant cell arteritis and rheumatoid arthritis, other common causes of a very high ESR include necrotizing vasculitis (inflammation of the blood vessel walls) and macroglobulinemia primary (cancer of the B lymphocytes, a type of white blood cell).


Though a low ESR is generally not a cause for concern, it is worth noting that liver or kidney disease, congestive heart failure and some protein abnormalities as well as sickle cell anemia or conditions that cause an increase in either red or white blood cells can cause a lower than normal ESR result. Medications such as aspirin, cortisone and quinine can also result in a lower ESR.

Discuss your ESR Test Results with a Doctor

Because there are so many conditions that can affect an ESR test, it is important to discuss your results with a qualified doctor who is aware of all your medical conditions and the medications you are taking. The ESR blood test is considered a screening test and cannot be used to diagnose any one condition. It is, however, useful in screening for certain inflammatory conditions, or in monitoring their progress.