The CRP test is sometimes used in patients with inflammatory bowel disease and some forms of arthritis and autoimmune diseases to assess how active the inflammation is and to monitor the treatment. The CRP test 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 ordered when acute inflammation is a risk (such as from an infection after surgery) or suspected based on patient symptoms. It is also ordered to help evaluate conditions, such as rheumatoid arthritis and lupus. The test may be repeated to determine whether treatment of an inflammatory disease is effective since CRP levels drop as inflammation subsides.

CRP also is used to monitor wound healing and to monitor patients who have surgical cuts (incisions), organ transplants, or burns as an early detection system for possible infections.

A high or increasing amount of CRP in your blood suggests that you have an acute infection or inflammation. In a healthy person, CRP is usually less than 10 mg/L. Most infections and inflammations result in CRP levels above 100 mg/L.

If the CRP level in your blood drops, it means that you are getting better and inflammation is being reduced.

When your results fall below 10 mg/L, you no longer have clinically active inflammation.

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.