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The erythrocyte sedimentation rate (ESR) blood test measures how quickly erythrocytes, a type of red blood cell, settle at the bottom of a test tube. It is also known as the sedimentation rate or sed rate test.
Red blood cells usually settle slowly, but inflammation causes them to settle more quickly. That means high ESR levels could be a sign of inflammation in your body.
A healthcare provider, such as a primary care physician or rheumatologist, may order the blood test if they suspect you have a condition that causes inflammation.
An ESR test helps determine how long it takes your red blood cells to settle at the bottom of a test tube. It helps indicate the presence of inflammation, your body’s response to infection, injury, or conditions such as immune system disorders and blood diseases.
Inflammation can cause your red blood cells to clump together, affecting how quickly they sink to the bottom of a test tube. Inflammation can also increase levels of certain proteins that may lead to clumping and the settling of red blood cells.
Your healthcare provider may recommend an ESR test if you have symptoms that indicate inflammation in your body, including:
- Headache
- Loss of appetite
- Unexpected weight loss
- Unexplained fever
- Joint stiffness
- Neck or shoulder pain
You do not need any special preparations for an erythrocyte sedimentation rate test. However, if you’re getting other blood tests that require fasting done at the same time, you may need to avoid eating or drinking.
The test usually takes place at your healthcare provider’s office or a diagnostic laboratory. You may want to wear a short-sleeved or loose-fitting shirt on the day of the test for easy access to your arm.
You can bring a family member or friend on the day of the test, especially if blood tests make you anxious. Talk to your healthcare provider about any medications or supplements you’re taking to see if you should continue taking them as usual.
If you have insurance, you should ask your insurance provider whether they will be covering the cost of the test or if you will need to pay out of pocket.
An ESR test involves drawing blood from a vein in your arm. This process usually takes less than five minutes.
After collection, the blood is sent to the laboratory, where a lab technician transfers it into a thin test tube and measures the rate at which the red blood cells settle to the bottom of the tube.
During the Test
During the test, a phlebotomist (a person trained in drawing blood) will ask you to sit comfortably in a chair before drawing blood from a vein in your arm. During an ESR test blood draw, the provider will do the following:
- Clean the area of your arm where they’ll be inserting the needle with an antiseptic
- Put pressure with a band on the upper arm to increase blood flow
- Insert the needle into the vein and collect blood into an airtight vial attached to the needle
- Remove the needle and band from the arm
- Put a bandage on the needle site
The provider will then send the blood sample to a laboratory, where a lab technician transfers it to a thin test tube and measures the rate at which the red blood cells settle.
After the Test
You can go home almost immediately after the test. If blood tests sometimes make you feel dizzy, consider asking a family member or friend to drive you home. Your healthcare provider may also advise you not to perform any heavy lifting for 24 hours after the test.
An ESR test, like any other blood test, is generally safe and does not lead to complications. You may experience slight pain or bruising at the needle site, but these symptoms go away quickly.
When your red blood cells settle to the bottom of the test tube, part of your blood, called plasma, will sit at the top of the tube. Once an hour has passed, the lab technicians will measure how much plasma is present. The result will be reported in millimeters per hour.
The results of an ESR test are often available within a couple of days. They may be available through the testing center’s online portal, or your healthcare provider may request that you contact or visit them for the results.
Interpreting Your Results
An ESR test cannot confirm the diagnosis of a medical condition. It can only reveal the level of inflammation in your body. If your ESR test shows abnormal levels, your provider will likely ask details about your health history and do a comprehensive physical exam.
The normal range for ESR can vary based on the laboratory. The normal range for ESR is usually higher in females and increases with age. The normal range of ESR for different groups is as follows:
| Sex and age | Normal range |
| Males younger than 50 years | Less than 15 millimeters per hour (mm/hr) |
| Females younger than 50 years | Less than 20 mm/hr |
| Males older than 50 years | Less than 20 mm/hr |
| Females older than 50 years | Less than 30 mm/hr |
| Children | Less than 10 mm/hr |
If your ESR falls outside the normal range, it doesn’t necessarily mean you have an inflammatory condition. Factors such as pregnancy or tilted ESR tubes may affect your results.
High ESR
A higher-than-normal ESR may suggest you have inflammation somewhere in your body. This could be due to any of the following conditions:
- Anemia
- Kidney disease
- Thyroid disease
- Infections
- Heart disease
- Inflammatory bowel disease (IBD)
- Systemic lupus erythematosus (SLE, or lupus)
- Low levels of the protein albumin
- Systemic vasculitis, the inflammation of blood vessels
Extremely high levels of ESR—greater than 100 millimeters per hour—may indicate one of the following conditions:
- Multiple myeloma: A blood cancer that develops in plasma cells in the bone marrow
- Lymphoplasmacytic lymphoma: A type of non-Hodgkin lymphoma
- Hypersensitivity vasculitis: An extreme reaction to a drug or infection that leads to inflammation and damage to the skin’s blood vessels
- Polymyalgia rheumatica: An inflammatory condition that causes pain and stiffness in the neck, shoulder, and hip
- Giant cell arteritis: Inflammation of the arteries, especially those in the head and neck
- Venous thromboembolism: A blood clot in a vein
- Infection: These can include pneumonia, bacteremia, or cellulitis
Low ESR
A lower-than-normal ESR can occur due to one of the following conditions:
- Polycythemia: Too many red blood cells
- Sickle cell disease: A condition where red blood cells are not shaped correctly
- Macrophage activation syndrome: A life-threatening complication of rheumatic disease, especially systemic juvenile idiopathic arthritis
- Heart failure: When the heart doesn’t pump blood as well as it should
- Abnormal fibrinogen levels: Dysfunctional or low levels of the protein
Erythrocyte sedimentation rate (ESR) is a blood test that can detect the presence of inflammation in your body.
A high ESR can indicate inflammation, and a low ESR may also be a sign of a condition that requires treatment. However, abnormal ESR levels do not always mean there’s an underlying condition.
Talk to your healthcare provider to discuss your test results and what they might mean.
