Blood test
ESR Test
An ESR test measures how quickly red blood cells settle in a tube. A faster rate suggests inflammation, so it is used to help detect and monitor inflammatory conditions.
Quick answer
ESR Test: what it is and what the results mean
The erythrocyte sedimentation rate (ESR) is a simple blood test that measures how far red blood cells fall in a tube over an hour. Inflammation makes the cells clump and settle faster, so a higher rate suggests inflammation in the body.
- Why it is done: It is used to help detect and monitor inflammatory and infective conditions, and is particularly useful in some specific illnesses such as polymyalgia rheumatica and giant cell arteritis.
- Understanding results: A raised ESR indicates inflammation but, like CRP, does not identify the cause.
What it is
The erythrocyte sedimentation rate (ESR) is a simple blood test that measures how far red blood cells fall in a tube over an hour. Inflammation makes the cells clump and settle faster, so a higher rate suggests inflammation in the body.
Why it is done
It is used to help detect and monitor inflammatory and infective conditions, and is particularly useful in some specific illnesses such as polymyalgia rheumatica and giant cell arteritis.
What to expect
A routine blood sample is taken from the arm; no fasting is required.
Understanding the results
A raised ESR indicates inflammation but, like CRP, does not identify the cause. It can also rise with age, in anaemia and in pregnancy, so results are interpreted carefully alongside symptoms and other tests.
Good to know
Risks and limitations
Risks are those of a routine blood test. Because many things affect the ESR and it is non-specific, it is used as a clue rather than a diagnosis and is often combined with a CRP.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
ESR Test: frequently asked questions
What does a high ESR indicate?
A high ESR suggests inflammation in the body, but it cannot say where or why on its own. It is interpreted alongside your symptoms, examination and other tests such as CRP.
Can a normal ESR rule out disease?
Not completely. Some conditions can be present with a normal ESR, so a single normal result does not exclude illness. Your clinician considers the whole picture.
Related tests
Other blood test investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- Royal College of Pathologists / relevant professional body
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