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What Is a Sedimentation Rate Blood Test and What It Tells You

Medically Approved by Dr. Edward Salko

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A sedimentation rate blood test or SED rate test confirms inflammatory activity in the body. It’s also known as an ESR blood test, which stands for erythrocyte sedimentation rate. Your doctor will most likely request this test if you exhibit symptoms of inflammation caused by infections. It could also be part of a routine checkup to assess your risk for heart disease and other severe conditions. 

Read more about what is a sedimentation rate blood test and what it means to have test results outside the normal range. 

What Is a Sedimentation Rate Blood Test?

A SED blood test or ESR test helps determine the degree of inflammation by analyzing how fast your red blood cells or erythrocytes settle in a vertical tube. However, an ESR blood test is not a sufficient independent diagnostic tool. 

While it aids in analyzing the nature of the inflammatory condition, you will need other tests to determine its cause. For example, if the chronic inflammation is due to an autoimmune disease, your doctor will assess the condition based on your other symptoms and the results of autoimmune disorder tests

Another lab test that goes hand-in-hand with an ESR test is the C-reactive protein (CRP) blood test. This detects acute inflammation and tissue injury as well as monitors if the treatment works. 

When Should You Take a Sedimentation Rate Blood Test

Your doctor may require you to take a SED rate blood test if you exhibit symptoms of inflammation associated with medical conditions, such as rheumatoid arthritis, systemic vasculitis, temporal arteritis, polymyalgia rheumatica, chronic infection, and lupus. These symptoms include the following:

  • Fever
  • Chills 
  • Fatigue 
  • Pelvic pain
  • Headaches
  • Loss of appetite 
  • Muscle stiffness 
  • Sudden weight loss
  • Neck and shoulder pain
  • Joint pain, stiffness, and swelling

Inflammation is a natural immune response to threats like pathogens or disease-causing microbes. In some cases, it can develop due to defects developed by the immune system. This leads to the immune cells attacking healthy cells resulting in autoimmune disease. 

When inflammation persists, it could be a sign of a severe health condition requiring immediate medical attention. On top of that, it comes with various discomforting effects, such as pain and swelling, which could impede your productivity and wellness. 

How Is the Test Done?

For medical technicians to perform the ESR blood test, a sample of whole blood must be extracted. For this reason, you will have to visit a proper medical facility where a phlebotomist can collect sufficient blood. Generally, you don’t need special preparation like fasting before the blood collection. However, it’s best to consult your doctor regarding skipping certain medications. 

Your blood sample will be placed on a tube following the modified Westergren sedimentation method. After filling the tube, it will be inverted eight to ten times. When the tube stays still, the erythrocytes or RBCs will begin to settle down on the bottom, leaving a clear plasma on top. 

The rate of erythrocyte fall or sedimentation becomes the basis for the test results. Red blood cells descend faster when the blood sample contains many proteins acting as acute phase reactants like CRPs, which are markers of inflammation.  

Test Results: High vs Low Sedimentation Rate

The results of the ESR blood test will be shown on the report in millimeters per hour (mm/hr). The value depicts the distance covered by the red blood cells clumping and sinking to the bottom of the tube within one hour. You can match your result to the normal reference interval indicated on the report. The normal SED rate range is from 0 to 32 mm/hr. 

While the blood test provides substantial information about inflammation, the result accuracy can be affected by certain conditions such as pregnancy, old age, thyroid disease, kidney disease, and some cancers. Hence, your doctor may include specific blood tests before requesting for a sedimentation rate blood test. Additionally, certain medications can also contribute to the increased SED rate.

What Does It Mean if Your Sedimentation Rate Is High?

A high SED rate is any value above 32 mm/hr. This entails a faster-than-normal rate of descent for the red blood cells, which suggests inflammation. The cause of the inflammation can range from an infection, injury, kidney disease, and heart disease to autoimmune disorders such as rheumatoid arthritis and vasculitis. 

Getting a high SED rate warrants further testing to identify the condition’s cause. Consequently, this would allow your healthcare provider to prescribe the proper treatment. 

What Does a Low Sedimentation Rate Mean?

A low SED rate entails slow sedimentation. While this does not generally cause any concerns, those with blood cell disorders often have extremely low ESR test values. These disorders include RBC deformities, sickle-cell anemia, leukocytosis (high white blood cells), and hypofibrinogenemia (extremely low fibrinogen). Speak to your doctor to get the appropriate diagnostic tests. 

Treatment for Abnormal Sedimentation Rate

To stabilize your ESR rate may require medication and lifestyle adjustments. However, to get the most out of treating abnormal sedimentation rate, the cause of the inflammation should be accurately identified. 

How Do You Treat High SED Rate?

A high SED blood test value can be lowered by giving up unhealthy foods and switching to nutritious foods, getting regular exercise, maintaining a healthy weight, and avoiding heavy drinking as well as smoking. Additionally, your doctor may also prescribe anti-inflammatory drugs depending on the disorder associated with the increased ESR. 

If it was due to an infection, treating the bacterial or viral infection can treat a high SED rate. On the other hand, if the condition’s cause is an underlying health complication, the long-term treatment may include drug prescription, therapy, etc.  

How Do You Treat Low SED Rate?

An extremely low SED rate is typically an effect of a blood disorder. Treating the abnormal ESR rate will not suffice. Your doctor will focus on the disease which causes the condition. If your decreased SED rate is due to leukocytosis, your doctor will determine the correct treatment. 

Pro Tip: While a low SED rate is typically not as alarming as a high SED rate, it still provides substantial insight into your blood health. You can further understand how well your blood cells are when you take a complete blood count (CBC). It’s inexpensive, accessible, and highly valuable for your wellness. 

Other Frequently Asked Questions

When should I worry about my ESR?

To get an ESR rate over 100 mm/hr should already cause an alarm. While going beyond the normal range suggests health issues related to inflammation, an extremely high ESR rate entails severe medical conditions such as cancer, heart disease, and untreated infections. Consult your doctor to secure other diagnostic procedures. 

Does lupus cause a high SED rate?

People diagnosed with systemic lupus erythematosus usually have a high SED rate. Although this is associated with its autoimmune nature, it can also be due to factors, such as infections. After all, infections, ranging from pneumonia to sepsis, are common among patients with lupus. 

What medications affect the SED rate? 

Anti-inflammatory drugs lower the SED rate. However, other medications and supplements can also affect the SED rate, which is why it’s best to let your healthcare provider about taking specific drugs. These drugs include quinine, cortisone, methyldopa, theophylline, vitamin A supplement, and birth control pills.

The Bottom Line

Your SED rate reveals essential information about your health as far as inflammation is concerned. While the immune activity is a natural and necessary reaction to ensure tissue repair and prevention of diseases, recurring and long-term inflammation can lead to further complications. By taking and understanding what is SED rate test, you can protect and restore your health and wellness. 

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