A c-reactive protein test measures the level of c-reactive protein (CRP) in your blood. CRP is a protein made by your liver. It's sent into your bloodstream in response to inflammation. Inflammation is your body's way of protecting your tissues if you've been injured or have an infection. It can cause pain, redness, and swelling in the injured or affected area. Some autoimmune disorders and chronic diseases can also cause inflammation.

Normally, you have low levels of c-reactive protein in your blood. High levels may be sign of a serious infection or other disorder.