A C-reactive protein (CRP) test measures the level of CRP in a sample of your blood. CRP is a protein that your liver makes, and its levels increase when there is inflammation in the body. The test can be used to help diagnose or rule out certain conditions, including infections from bacteria or viruses, inflammatory bowel disease, disorders of the intestines that include Crohns disease and ulcerative colitis, autoimmune disorders such as lupus, rheumatoid arthritis, and vasculitis, and lung diseases such as asthma. It can also be used to monitor people after surgery or other invasive procedures to check for infection during their recovery period. A high-sensitivity CRP test (hs-CRP) is more sensitive than a standard CRP test and can find smaller increases in CRP protein than a standard test can. The hs-CRP test can help show the risk of getting coronary artery disease, and a high level of hs-CRP in the blood has been linked to an increased risk of heart attacks. However, the test cannot show what is causing the inflammation or which part of your body is inflamed.