CRP is used to identify the presence of inflammation, to determine its severity, and to monitor response to treatment. A more sensitive form of the test, C-reactive protein high sensitivity (hsCRP), is used to assess your risk of heart disease.
When it is suspected that you might be suffering from an inflammatory disorder (as with certain types of arthritis and autoimmune disorders or inflammatory bowel disease) or to check for the possibility of infection (especially after surgery).
A blood sample taken from a vein in the arm.
Quick Read patient information sheet
C-reactive protein (CRP) is a protein made by the liver and secreted into the blood. It is often the first evidence of inflammation or an infection in the body. Its concentration increases in the blood within a few hours after the start of infection or other inflammatory injury. The level of CRP can increase many hundred-fold in response to inflammation and then drop relatively quickly as soon as the inflammation passes, making it a valuable test to monitor effectiveness of treatment.
A blood sample is obtained by inserting a needle into a vein in your arm.
No test preparation is needed.
CRP is often measured in patients with inflammatory diseases, such as some forms of arthritis and autoimmune diseases or in inflammatory bowel disease. It is used to assess how active the inflammation is and to monitor the treatment. CRP is also used to monitor patients after surgery or other invasive procedures to detect the presence of an infection during the recovery period. CRP tests are not specific enough to diagnose a particular disease. Rather, CRP is a general marker of infection and inflammation that alerts medical professionals that further testing and treatment may be necessary.
Because CRP increases in cases of inflammation, the test is requested when acute inflammation is a risk (such as from an infection after surgery, or other trauma) or suspected based on someone's symptoms. It is also requested to help diagnose and monitor treatment of chronic inflammatory conditions, such as rheumatoid arthritis and lupus. The test may be repeated often to learn whether treatment of an inflammatory disease is effective since CRP levels drop as inflammation subsides.
A high or increasing amount of CRP in your blood suggests that you have an acute infection or inflammation - most infections and inflammations result in CRP levels above 10 mg/L.
If the CRP level in your blood drops, it means that you are getting better and inflammation is being reduced.
Another test to monitor inflammation is called the erythrocyte sedimentation rate (ESR). Both tests give similar information about the presence of inflammation. However, CRP appears and then disappears sooner than changes in the ESR. Thus, your CRP level may fall to normal if you have been treated successfully, such as for a flare-up of arthritis, but your ESR may still be abnormal for a while longer.
C-reactive protein high sensitivity (hsCRP); erythrocyte sedimentation rate (ESR)
Conditions: Arthritis, autoimmune disorders
RCPA Manual: C-reactive protein (CRP)
Medline Plus: C-reactive protein
Mayo Clinic: C-reactive protein test
Last Review Date: September 20, 2022