Blood test results

High ESR (Sed Rate)

The ESR, or sed rate, measures how quickly red blood cells sink to the bottom of a tube in an hour. Inflammation makes them clump and fall faster. It’s an old, simple test that says “something’s up” without saying what.

Quick answer: Normal ESR rises with age and is higher in women: a rough upper limit is age ÷ 2 for men and (age + 10) ÷ 2 for women. Mild rises are common with infection, anaemia, pregnancy and kidney disease. Over 100 mm/hr usually has a serious cause and needs prompt investigation.

What the test measures

Blood is left to stand in a tall tube, and the lab measures how far the red cells fall in one hour, in millimetres. Inflammation raises proteins such as fibrinogen and antibodies, which make red cells stack and sink faster. ESR rises and falls more slowly than CRP, over days to weeks.

Typical adult ranges

What a high result usually means

Common causes:

Less common but important:

ESR over 100 mm/hr almost always has a cause: infection is the most common, followed by autoimmune and vasculitis conditions, cancer and kidney disease. No cause is found in fewer than 2 in 100 people.

Symptoms

ESR causes no symptoms itself. The cause might: fever, joint pain or stiffness, shoulder and hip stiffness in the morning, headache, bone pain, weight loss, night sweats or tiredness.

What happens next

See a doctor the same day if you’re over 50 with a new headache, scalp tenderness, pain in the jaw when chewing, or any change in vision (blurring, double vision or loss): giant cell arteritis can cause permanent sight loss, and treatment shouldn’t wait for test results. Sudden vision loss needs emergency care. See your GP within days for new stiffness in both shoulders or hips with a raised ESR, or an ESR over 100 with weight loss, bone pain or night sweats.

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Common questions

What is a dangerous ESR level?

There’s no single dangerous number, but an ESR over 100 mm/hr almost always has a significant cause, such as infection, vasculitis, an autoimmune condition, cancer or kidney disease, and needs prompt investigation.

Is an ESR of 30 high?

It depends on your age and sex. A rough upper limit is age ÷ 2 for men and (age + 10) ÷ 2 for women, so 30 can be normal for a woman in her 60s but is high for a man in his 30s.

Can ESR be high without disease?

Yes. Older age, being female, anaemia, pregnancy, kidney disease and obesity can all raise ESR. A recent infection can keep it raised for weeks.

What’s the difference between ESR and CRP?

Both measure inflammation. CRP rises and falls within days, so it tracks acute illness better. ESR changes more slowly and is affected by more things, such as age and anaemia, but it’s useful in giant cell arteritis, polymyalgia rheumatica and myeloma.

Does a high ESR mean cancer?

Usually not. Most raised ESRs come from infection, inflammation, anaemia, age or pregnancy. A very high ESR, especially with weight loss, bone pain or anaemia, does need checking for cancers such as myeloma.

How long does ESR stay high after an infection?

Often several weeks. ESR falls more slowly than CRP, so it can still be raised after you feel better. A repeat test 4–6 weeks later usually shows it coming down.

Evidence and more information

Updated 8 November 2026. General education, not personal medical advice. Reference ranges differ between laboratories, so use the range printed on your own report and talk to your GP about your result.

Related

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