Inflammation
ESR blood test: what a high or low result means
What an ESR (sed rate) result means, why ESR can be high, and what to ask your doctor.
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Explain my results → Available on web, iOS & Android.What is ESR?
ESR, or erythrocyte sedimentation rate, measures how quickly red blood cells settle to the bottom of a tube of blood. When there is inflammation, proteins in the blood make the red cells clump together and settle faster, giving a higher ESR. In the US it is often called the sed rate. Like CRP, it shows that inflammation is present but not where or why.
Why is this test done?
- To check for inflammation
- To help diagnose and monitor conditions such as polymyalgia rheumatica and giant cell arteritis
- To monitor some forms of arthritis
- As part of investigating unexplained symptoms
What does a high ESR mean?
A high ESR suggests inflammation, but it can also rise for reasons unrelated to inflammation.
Possible reasons include:
- Infection
- Inflammatory and autoimmune conditions, such as rheumatoid arthritis and polymyalgia rheumatica
- Older age, as ESR naturally rises with age
- Anaemia
- Pregnancy
- Kidney disease
- Some blood conditions, such as myeloma
What does a low ESR mean?
A low ESR is usually normal and not a concern.
Possible reasons include:
- Normal variation
- Some blood conditions that change the shape or number of red cells, such as polycythaemia or sickle cell disease
When to get help quickly. If you are over 50 and develop a new headache, a tender scalp, jaw pain when chewing or any change in your vision, seek medical help the same day, as these can be signs of giant cell arteritis, which needs prompt treatment to protect your sight.
Why we don't list a "normal range". Reference ranges differ between laboratories and can depend on your age, sex and whether you are pregnant. The range printed next to your result on your own report is the one that applies to you, so use that, and talk to your doctor about what your result means for you.
What can affect your ESR result?
- Age and sex, as ESR is higher in older people and women
- Anaemia
- Pregnancy
- Delays in testing the sample
Make sense of the whole report, not just one line
Results are easier to understand together. Patiently AI explains your report as a whole and writes personalised questions for your next appointment.
Try it with your own results → Paste, upload or photograph your results.Questions to ask your doctor
- What might be causing my raised ESR?
- Was my CRP checked too?
- Do I need further tests?
- When should it be repeated?
Frequently asked questions
Why is ESR higher in older people?
ESR naturally rises with age, so a result that would be high for a young person may be normal for an older person. Labs and doctors take age into account.
Is ESR the same as CRP?
No, but both measure inflammation. CRP changes faster, while ESR changes slowly over weeks and is affected by more factors.
Can anaemia affect ESR?
Yes. Having fewer red cells lets them settle faster, which can raise ESR even without inflammation.
Can Patiently AI explain my ESR result?
Yes. Paste your results, or upload a photo, PDF or Word file, and Patiently AI explains them in plain English, sticking to the numbers and ranges on your own report rather than adding its own, and suggests questions to ask your doctor. It is free, needs no account, and removes identifying details on your device first.