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Erythrocyte sedimentation rate (ESR) blood test

5-minute read

Key facts

  • An erythrocyte sedimentation rate (ESR) blood test checks how fast red blood cells settle, to help detect inflammation in your body.
  • The test does not show the cause or location of inflammation, so doctors usually use it along with other tests to help diagnose medical conditions.
  • A high ESR result may suggest infection, an inflammatory disease or some types of cancer.
  • It is important to speak with your doctor to understand your results.

What is an erythrocyte sedimentation rate blood test?

An erythrocyte sedimentation rate (ESR) blood test checks how fast red blood cells sink to the bottom of a test tube. If they fall faster than normal, it may mean there is inflammation in your body.

Inflammation is your body's response to injury, irritation or infection.

When is an ESR blood test used?

Your doctor may order an ESR blood test along with other tests to check for:

This blood test does not show the exact cause or location of a problem. Other tests are needed to find the location and cause of the inflammation, infection or cancer.

ESR blood tests are especially useful for detecting conditions including:

If you have one of these conditions, your doctor may also use ESR blood tests to monitor your response to treatment.

Where can I get an ESR blood test?

You usually need to go to a pathology collection centre with a referral from your doctor. Your doctor will recommend one near you.

Sometimes, your doctor will collect blood for testing in their clinic. Blood tests are also routinely done in hospitals.

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How do I prepare for an ESR blood test?

There is no special preparation needed for an ESR blood test.

However, if you are having other blood tests done at the same time, you may need to prepare. Check with your doctor or the pathology collection centre if there is anything you need to do before your blood test.

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What happens during an ESR blood test?

A health professional will take a sample of blood, usually from a vein in your arm. The blood will then be sent to a laboratory for testing.

How does an ESR blood test work?

In an ESR test, the blood sample is placed into a tall, thin tube. The blood is allowed to settle and the 'sedimentation rate' is measured.

If there is inflammation, red blood cells stick to each other and form clumps. These clumps are heavier than normal red blood cells, so if there is inflammation, the red blood cells will clump together and fall more quickly to the bottom of the tube.

If there is no inflammation, the red blood cells will settle more slowly.

After some time, a layer of clear liquid (plasma, which has no red blood cells) forms at the top of the tube. The ESR measures the height of the clear plasma at the top of the tube.

What do my ESR blood test results mean?

A low ESR means that red blood cells settle slowly, which suggests there is no inflammation.

A high ESR means that many red blood cells have settled quickly, which may suggest:

ESR may be higher due to older age, pregnancy or anaemia. Some medicines may also affect your ESR result.

In some conditions, such as sickle cell disease, ESR levels can be very low.

It is important to talk to your doctor about your results so they can explain what they mean for you.

Resources and support

Pathology Tests Explained provides information about the ESR blood test.

Read our 'Guide to blood testing' to learn more about blood tests, including:

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.

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