Raised inflammatory markers (CRP and ESR)
What CRP and ESR actually measure, why a mildly raised result is so common, and when raised markers genuinely warrant a specialist look
Being told your inflammatory markers are raised is a common reason for worry and for referral to a rheumatologist. CRP and ESR are general measures of inflammation: they can tell a doctor that something may be stirring, but not what or where. On their own they are not a diagnosis, and a mildly raised result is very often harmless. This guide explains what these tests measure, why they rise, and when a raised result is worth a closer look.
Written for patients and reviewed by Dr Liubov Borukhson, Consultant Rheumatologist (GMC 7021928). Last clinically reviewed: June 2026.
What CRP and ESR actually measure
CRP (C-reactive protein) is a protein whose level in the blood rises in response to inflammation, so the test simply measures how much inflammation is present in general terms. ESR (erythrocyte sedimentation rate) is an older test that also helps assess levels of inflammation. Both are useful, but neither is specific: they do not tell the doctor where the inflammation is or what is causing it, which is why results have to be read alongside your symptoms, examination and other tests rather than in isolation.
The two markers behave slightly differently. CRP tends to rise and fall quickly, and is affected by fewer other factors. ESR is influenced by a number of things besides inflammation, including your age, anaemia and pregnancy, all of which can nudge it upwards without any underlying disease. For this reason a raised ESR in an older adult, or in someone who is anaemic, needs to be interpreted with particular care.
Why markers rise, and why a mild rise is common
Inflammatory markers can rise for a great many reasons, and most of them are not rheumatological. Common everyday causes include infections of all kinds, recent injury or surgery, and a wide range of benign and self-limiting conditions. Levels can also be temporarily raised after a viral illness and then settle on their own.
This is the reassuring part. A mildly raised CRP or ESR, found on its own in someone who feels well, is a common and often unimportant finding. It does not mean a serious disease is present, and frequently the most sensible response is a simple repeat test once any recent infection has passed, to confirm the level has settled.
Normal markers do not exclude inflammatory disease
Just as a raised result does not confirm disease, a normal one does not rule it out. This is an important and less well-known point. Some people with genuine inflammatory arthritis or another rheumatological condition have CRP and ESR that sit within the normal range, particularly early on or when only a few joints are involved. The markers are a supporting clue, not a gatekeeper.
This is why your symptoms carry more weight than any single blood result. Persistent joint pain, swelling or early-morning stiffness deserves proper assessment whether or not the markers are raised, and reassurance based on normal bloods alone can sometimes be misleading.
When raised markers warrant rheumatology assessment
A raised marker becomes more meaningful when it appears alongside symptoms that point towards inflammation in the joints or elsewhere. A specialist review is particularly worthwhile when a raised CRP or ESR comes together with:
- Persistent joint pain, swelling or warmth
- Early-morning stiffness lasting more than half an hour
- New shoulder or hip girdle stiffness in an older adult
- Marked fatigue, fevers, night sweats or unintended weight loss
- A raised result that persists on a repeat test rather than settling
A persistently or markedly raised marker, or one that does not have an obvious explanation, is also worth assessing in its own right, so that anything significant is not missed.
How a specialist interprets them, and when to seek review
A rheumatologist does not treat a number; the focus is on you. The assessment brings the result together with a careful history and examination, and with other tests where they help, to judge whether the markers reflect something that needs treating or simply a passing or incidental rise. Where joints are involved and the blood picture is equivocal, point-of-care ultrasound during the consultation can show whether true inflammation is actually present, which often settles the question in a single visit. You can read more on the point-of-care ultrasound page.
If you have been told your inflammatory markers are raised but you feel well, there is usually no cause for alarm, and a repeat test or a specialist review can put the result in context. Seek assessment more promptly if a raised result comes with persistent joint swelling, new girdle stiffness, or symptoms such as fevers, night sweats or weight loss. If you feel significantly unwell, contact your GP or NHS 111 rather than waiting for a routine appointment.
Common questions
What does a raised CRP or ESR result actually mean?
CRP and ESR are general measures of inflammation, so a raised result tells your doctor that something may be stirring, but not what is causing it or where it is. They are not a diagnosis on their own and have to be read alongside your symptoms, examination and other tests. A mildly raised result in someone who feels well is common and very often harmless.
Should I be worried, or is this serious?
A mild rise found on its own, with no symptoms, is usually not a cause for alarm and frequently settles by itself. Markers commonly go up after everyday things such as infections, recent injury or a viral illness, none of which are rheumatological. A raised result becomes more meaningful when it comes with joint pain, swelling, prolonged morning stiffness, or symptoms such as fevers, night sweats or weight loss, which deserve prompt assessment.
If my markers are normal, does that rule out arthritis?
No. A normal CRP or ESR does not exclude inflammatory disease, because some people with genuine inflammatory arthritis have markers that sit in the normal range, particularly early on or when only a few joints are involved. This is why your symptoms carry more weight than any single blood result. Persistent joint pain, swelling or early-morning stiffness deserves proper assessment whether or not the markers are raised.
How is the cause of a raised marker diagnosed?
A rheumatologist brings the result together with a careful history, an examination and other tests where they help, rather than treating a number in isolation. Where joints are involved and the blood picture is unclear, Dr Borukhson can perform point-of-care ultrasound during the consultation, which shows whether true inflammation is actually present and often settles the question in a single visit. If you feel well, a simple repeat test once any recent infection has passed is sometimes all that is needed to confirm the level has settled.
Told your inflammatory markers are raised?
A one-stop specialist assessment, with ultrasound where helpful, can explain what the result means for you and either offer reassurance or agree a clear plan
Book an appointment