You don’t need any special preparations for this test. But 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 to follow.
What Is Your Sedimentation Rate?
The sedimentation rate — or “sed rate,” for short — is a blood test that checks for inflammation in your body. It’s one clue for your doctor that you might have a disease linked to inflammation, like arthritis or cancer, or an infection.
The sed rate test measures how fast red blood cells fall to the bottom of a tube. Inflammation creates proteins that make red blood cells fall more quickly.
Another name for this test is erythrocyte sedimentation rate (ESR). Red blood cells are called erythrocytes. Sedimentation is the process by which they fall to the bottom of the tube.
Why You Might Get a Sed Rate
Your doctor might order the sed rate test if you have symptoms like these:
- Headaches
- Stiff, swollen, or painful joints
- Pain in your shoulders, neck, or pelvis
- Appetite loss
- Weight loss without trying
The sed rate test can be part of the process of discovering if you have one of these conditions:
- Infection (including of the bones)
- Cancer
- Arteritis (inflammation of the blood vessels)
- Lupus (an autoimmune disease that damages the skin, joints, and other parts of your body)
- Polymyalgia rheumatica (causes stiff and painful muscles)
- Rheumatoid arthritis (autoimmune disease in which the immune system attacks your joints)
- Systematic vasculitis (inflammation in your blood vessels)
You might also get this test once you’ve started treatment for one of these conditions. The sed rate can help your doctor see how well your body is responding to treatment.
Taking the Blood Sample
You don’t need to do anything special to prepare. It’s just a basic blood test.
Let your doctor know what medicines (and supplements) you take before you have the test. Certain drugs can affect the results. Also let your doctor know if you are pregnant or are having your period.
A nurse or other health care provider will take a sample of your blood, usually from a vein in your arm. They will first tie a band around the upper part of your arm to make your vein fill with blood and swell up. Then they’ll clean the area with an antiseptic, and place a needle into your vein. Your blood will collect into a vial or tube.
The process should only take a couple of minutes. Afterward, you’ll get a piece of gauze and a bandage over the area to stop the bleeding.
You may feel a slight sting as your blood is drawn. Afterward, you may have a small bruise. You might feel dizzy and sore, and there might be some bleeding.
The Results and What They Mean
Your sample will go to a lab. You should have the results in 1 or 2 hours.
A lab technician will place your red blood cells into a tall, thin tube and check how far they fall in 1 hour. When you have inflammation in your body, abnormal proteins in your blood make red blood cells form into clumps. These clumps are heavy, so they fall to the bottom of the tube more quickly than single blood cells.
The faster the blood cells sink, the more inflammation you have in your body.
The sed rate test reports in millimeters (mm) the distance between the clear liquid (plasma) at the top of the tube and your red blood cells after 1 hour. The normal range is:
- 0 to 15 mm/hour in men younger than 50
- 0 to 20 mm/hour in men older than 50
- 0 to 20 mm/hour in women younger than 50
- 0 to 30 mm/hour for women older than 50
A high sed rate is a sign you have a disease that causes inflammation in your body.
Some conditions and medicines can affect the speed at which red blood cells fall, and they may affect your test results. These include:
- Anemia
- Older age
- Kidney problems
- Thyroid disease
- Pregnancy or having your period
- Obesity
- Drugs like birth control pills, methyldopa (Aldomet), theophylline (Theo-24, Theolair, Elixophylline), vitamin A, cortisone, and quinine
Other Tests You May Need
The sed rate test can only tell your doctor that you have inflammation somewhere in your body. It can’t show where the inflammation is or what caused it. Your doctor may also test for your erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) to help make a diagnosis. Both are acute phase reactants or inflammatory markers which can help point to a diagnosis or help follow treatment in a diagnosis. You will still need imaging or even biopsyies to make a specific diagnosis.
Talk to your doctor about the results of your sed rate test, and any other tests you have. Make sure you understand what the results mean, and how they’ll affect your treatment.
Show Sources
American Association for Clinical Chemistry: “ESR.”
Mayo Clinic: “Sed rate (erythrocyte sedimentation rate): How you prepare,” “Overview,” “Results,” “Why it’s done.”
National Heart, Lung, and Blood Institute: “What to Expect With Blood Tests.”
Nemours Foundation: “Blood Test: Erythrocyte Sedimentation Rate (ESR).”
University of Rochester Medical Center: “Erythrocyte Sedimentation Rate.”
Erythrocyte Sedimentation Rate (ESR)
An erythrocyte sedimentation rate (ESR) is a blood test that that can show if you have inflammation in your body. Inflammation is your immune system’s response to injury, infection, and many types of conditions, including immune system disorders, certain cancers, and blood disorders.
Erythrocytes are red blood cells. 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 the red blood cells settle or sink to the bottom of the tube. Normally, 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 normal, it may mean you have a medical condition causing inflammation. The speed of your test result is a sign of how much inflammation you have. Faster ESR rates mean higher levels of inflammation. But an ESR test alone cannot diagnose what condition is causing the inflammation.
Other names: ESR, SED rate sedimentation rate; Westergren sedimentation rate
What is it used for?
An ESR test can be used with other tests to help diagnose conditions that cause inflammation. It can also be used to help monitor these conditions. Many types of conditions cause inflammation, including arthritis, vasculitis, infection, and inflammatory bowel disease. An ESR may also be used to monitor an existing condition.
Why do I need an ESR?
Your health care provider may order an ESR if you have symptoms of a condition that causes inflammation. Your symptoms will depend on the condition you may have, but they may include:
- Headaches
- Unexplained fever
- Weight loss
- Joint stiffness
- Neck or shoulder pain
- Loss of appetite
- Anemia
What happens during an ESR?
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Will I need to do anything to prepare for an ESR?
You don’t need any special preparations for this test. But 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 to follow.
Are there any risks to the test?
There is very little risk to having an ESR. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
What do the results mean?
Your provider will use the results of your ESR test along with your 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 may be from a condition that causes inflammation, such as:
- Arteritis
- Arthritis
- Systemic vasculitis
- Polymyalgia rheumatica
- Inflammatory bowel disease
- Kidney disease
- Infection
- Rheumatoid arthritis and other autoimmune diseases
- Heart disease
- Certain cancers
A low ESR test result means your red blood cells sank more slowly than normal. This may be caused by conditions such as:
- A blood disorder, such as:
- Polycythemia
- Sickle cell disease (SCD)
- Leukocytosis, a very high white blood cell count (WBC)
If your ESR results are not normal, it doesn’t always mean you have a medical condition that needs treatment. Pregnancy, a 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.
Is there anything else I need to know about an ESR?
Because an ESR can’t diagnose a specific disease, your provider may order other tests at the same time. Also, it’s possible to have a condition that causes inflammation and still have a normal ESR result. A C-reactive protein (CRP) test is commonly done with an ESR to provide more information.
References
- Cleveland Clinic: Health Library: Diagnostics & Testing [Internet]. Cleveland (OH): Cleveland Clinic; c2022. Sed Rate (Erythrocyte Sedimentation Rate or ESR) Test; [reviewed 2018 Mar 14; cited 2022 Mar 17]; [about 5 screens]. Available from: https://my.clevelandclinic.org/health/diagnostics/17747-sed-rate-erythrocyte-sedimentation-rate-or-esr-test
- Hinkle J, Cheever K. Brunner & Suddarth’s Handbook of Laboratory and Diagnostic Tests. 2nd Ed, Kindle. Philadelphia: Wolters Kluwer Health, Lippincott Williams & Wilkins; c2014. Erythrocyte Sedimentation Rate (ESR); p. 267-68.
- MDS Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co., Inc.; c2022. Lab Test: Erythrocyte Sedimentation Rate (ESR); [reviewed 2020 May; cited 2022 Feb 18]; [about 2 screens]. Available from: https://www.msdmanuals.com/en-pt/home/SearchResults?query=erythrocyte+sedimentation+rate#
- National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests; [ cited 2022 Mar 17]; [about 16 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests
- Testing.com [Internet]. Seattle (WA): OneCare Media; c2022. Erythrocyte Sedimentation Rate (ESR); [modified 2022 Jan 14; cited 2022 Mar 17]; [about 10 screens]. Available from: https://www.testing.com/tests/erythrocyte-sedimentation-rate-esr/
- Tishkowski K, Gupta V. Erythrocyte Sedimentation Rate. [Updated 2021 May 9; cited 2022 Mar 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557485/
- University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2022. Health Encyclopedia: Erythrocyte Sedimentation Rate; [cited 2022 Mar 17]; [about 4 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=erythrocyte_sedimentation_rate
Related Health Topics
- Arthritis
- Autoimmune Diseases
- Crohn’s Disease
- Polymyalgia Rheumatica
- Ulcerative Colitis
- Vasculitis
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