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Plain-language information for patients

What is a CRP test?

CRP, or C-reactive protein, is a substance made by the liver that rises in the blood when there is inflammation anywhere in the body — for example from infection, injury or a flare of an inflammatory condition.

What does a high CRP mean?

A raised CRP tells your doctor that inflammation is present, and roughly how much, but not where it is coming from. Bacterial infections often cause high levels; mild rises can come from many causes including viral illness, injury and chronic conditions.

Because it is non-specific, CRP is interpreted alongside your symptoms, examination and other tests — it is a clue, not a diagnosis.

Why is it sometimes repeated?

CRP changes quickly, so the trend over time is useful: a falling level can suggest an infection is improving or responding to treatment, while a rising level may prompt a closer look.

A separate, very sensitive version (hs-CRP) is sometimes used to help assess cardiovascular risk, which is a different purpose from checking for infection.

Common questions

Does a normal CRP rule out infection?

Not always — CRP can be normal early in an illness or with some infections. Doctors interpret it together with your symptoms and other findings.

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This page is general information, not personal medical advice, and does not replace a consultation with a qualified health professional. If you are worried about your health, please speak to your GP, pharmacist, or another clinician. Last reviewed 2026-06-08.