What it measures
C-reactive protein (CRP) is made by the liver, and its level rises quickly with inflammation or infection. The standard test reads the higher levels seen with illness; a high-sensitivity version (hs-CRP) reads much lower levels.
Why people test it
- Checked when an infection or inflammation is suspected, to see how active it is.
- Monitored in long-term inflammatory conditions, such as rheumatoid arthritis or inflammatory bowel disease.
- Repeated to follow how an infection or a flare settles over time.
Typical range
Ranges vary between labs, with the method used, age and sex, and your report shows the lab's own range. One NHS lab gives below 5 mg/L as its reference range. Source: North Bristol NHS Trust, Severn Pathology: CRP.
Finger-prick or vein?
A finger-prick sample is usually fine for CRP. A vein draw works too and is used when it is part of a larger panel.
A recent infection, injury or very hard exercise can raise CRP for a while, so a result taken then may not show the usual level.