Key takeaways
- ESR (erythrocyte sedimentation rate) is a general marker of inflammation somewhere in the body.
- Age and anaemia also nudge ESR upwards, so a result is always read in context.
- ESR moves slowly, both up and back down, which makes it good for tracking a condition over weeks or months.
- A raised ESR gives a doctor a reason to look for the cause alongside your symptoms.
Your doctor has asked for an ESR, or your results show one flagged as raised, and the name tells you very little. Erythrocyte sedimentation rate sounds far more complicated than it is.
ESR measures how quickly red blood cells settle to the bottom of a sample tube over an hour. They settle faster when certain proteins linked to inflammation are raised in your blood. It is a general marker that covers many conditions at once. You can book an ESR blood test at Blood London without a GP referral.
If you already know you need one, book an ESR blood test at 117a Harley Street. It costs £43.75 plus the £50 blood draw, with results in 1 day.
What does the ESR test actually measure?
ESR measures how far red blood cells fall through plasma in an upright tube over one hour. When inflammation is present, certain proteins make red cells clump together and settle faster. So a higher ESR broadly reflects more inflammation somewhere in the body.
It is one of the oldest blood tests still in routine use, valued because it is simple, cheap and widely available. What it cannot do is say what is causing the inflammation, or where it is.
What can cause a raised ESR?
Anything from a minor infection to a long-term inflammatory condition can raise ESR. So can factors that have nothing to do with illness. ESR rises with age, tends to run higher in women than men, and goes up with anaemia, pregnancy and obesity, with or without inflammation.
Because it is so general, a raised ESR works best as a prompt to look further. It is also useful for tracking how a known inflammatory condition is behaving over time.
How is ESR different from CRP?
| Feature | ESR | CRP |
|---|---|---|
| What it reflects | Red cell settling rate, affected by inflammation-related proteins | Direct measurement of a protein made by the liver in response to inflammation |
| Speed of change | Rises over days and can take weeks to settle | Rises and falls quickly, over hours to days |
| Affected by age or anaemia | Yes, independently of inflammation | Less affected by age or anaemia |
| Typical use | Monitoring a known condition over time | Picking up or tracking a more acute change |
At Blood London, CRP can be booked alongside ESR when a doctor wants both a fast-changing and a slow-changing marker of inflammation. It costs £70, with results in 1 day. Our guide to what a CRP result means covers that test in more detail.
Why does ESR change so slowly?
ESR depends on proteins that take time to rise and fall in the blood. It also measures an indirect effect of those proteins, the settling of red cells, instead of counting them directly. So ESR can stay raised for some time after an infection has cleared, and it can lag behind how someone actually feels.
That is one reason ESR is often used to track a chronic or ongoing condition over weeks or months. It is less suited to catching a sudden change from one day to the next.
When do doctors use an ESR test?
ESR typically supports the assessment of unexplained symptoms such as persistent fatigue, joint pain or stiffness, or unexplained weight loss. It is also used to monitor a condition that is already being managed, where the trend over time matters more than any single result.
It is rarely, if ever, used by itself to diagnose a specific condition. A doctor will usually order it with a full blood count and other relevant tests.
Some symptoms need a doctor sooner. If you are over 50 and have a new headache, scalp tenderness, jaw pain when chewing or any change in your vision, see a doctor the same day. This can be a sign of giant cell arteritis, which needs urgent treatment. Unexplained weight loss, night sweats or persistent bone pain also mean seeing a doctor promptly.
How testing works at Blood London
You can walk in or book online at 117a Harley Street, seven days a week, with no GP referral and no fasting needed. Results are usually back within 1 day and sent to you by email.
For a broader starting picture in one visit, the Haematology Profile pairs a full blood count with ESR for £75. Results also take 1 day. Each test price on this page is plus the £50 blood draw, as with all our private blood tests in London. When you are ready, start your booking.
Frequently asked questions
Does a raised ESR mean I have an infection?
Not necessarily. A raised ESR reflects inflammation somewhere in the body. Infection is one cause, but so are chronic conditions, anaemia, age and pregnancy.
Why would a doctor order both ESR and CRP?
They change at different speeds: CRP reflects more recent change, while ESR shows a slower-moving trend, so together they give a fuller picture.
Can ESR be raised in a healthy person?
Yes. ESR naturally rises with age and can be affected by anaemia, pregnancy or obesity. A mildly raised result in someone who is otherwise well is not automatically a cause for concern.
Is ESR the same as a full blood count?
They are separate tests. ESR is a single measurement of inflammation, while a full blood count counts red cells, white cells and platelets. They are often requested together.
How quickly will I get my ESR result?
Results are usually available within 1 day, sent to you by email as a laboratory report showing the result against its reference range.
Should I see a doctor if my ESR is raised?
Yes, particularly if you also have persistent fatigue, joint pain or unexplained weight loss. A doctor can discuss what further assessment might help. You can also add a doctor review of your report to your test for £75.
References
- NHS: Blood tests
- Lab Tests Online UK: ESR (erythrocyte sedimentation rate)
- NHS: Giant cell arteritis
- NICE CKS: Giant cell arteritis
- NHS: Polymyalgia rheumatica