In brief
A blood test for C-reactive protein, a protein the liver releases into the blood in response to inflammation.
What it measures
C-reactive protein (CRP), measured in mg/L. A high-sensitivity version, hsCRP, is used to assess heart disease risk.
Why it is done
To look for infection, including after surgery, and to help diagnose and monitor autoimmune diseases such as rheumatoid arthritis and lupus, and inflammatory bowel diseases such as Crohn's disease.
Reading the results
- Most infections and inflammations cause CRP levels above 10 mg/L.
- A rising level suggests an active infection or inflammation, and a falling level suggests it is settling.
- The CRP level often does not match how severe the inflammation is.
Results can vary between laboratories, so repeat tests are best done at the same laboratory.
Reference ranges
| Result | Range |
|---|---|
| Infection or inflammation | Usually above 10 mg/L |
Ranges differ between laboratories. Always compare a result with the range printed on your own report, and ask your doctor what it means for you.
Before the test
Ask your doctor whether you need to fast or stop any foods or supplements.
What can affect the result
- Some medicines
- Testing at different laboratories
Related topics
Connections
C-reactive protein (CRP) measures
CRP levels start to rise soon after inflammation affects the body, such as through an injury or an infection.
- Chronic low-grade inflammation Supported
CRP is used to help diagnose and monitor autoimmune diseases and inflammatory bowel disease.
Sources
Test information summarised from the sources listed on this page, read on 19 October 2026. General education only, not medical advice. Spotted a mistake? Please tell us through the HuBu-Intel contact page.