A C-reactive protein test is a medical procedure that measures the amount of C-reactive protein in the body. It is a form of protein in the blood released by the liver to respond to inflammatory activities. When an injury occurs or when the body is attacked by toxic substances, bacteria, or viruses, the immune system works by sending cytokines and inflammatory cells. This leads to redness, bruising, swelling, and pain. Results of a C-reactive protein test can help determine the presence of a serious infection or inflammatory condition. 
You can take the C-reactive protein test at home by collecting a blood sample yourself and then sending to a lab for further analysis. In general, you draw the blood from the fingertip with a very small needle. Blood is applied to a special paper that will be processed later by the laboratory. You can easily purchase at-home tests over the counter. However, it is advisable to have it done in a medical center to ensure safety and proper interpretations.