C-reactive protein (CRP) is a substance produced by the liver in response to inflammation in the body. It is part of the immune system and helps to identify and respond to infections or injuries. Elevated levels of CRP can indicate various conditions, including infections, autoimmune diseases, and chronic inflammatory conditions. Doctors often measure CRP levels through a blood test to assess inflammation. High CRP levels may prompt further investigation to determine the underlying cause. This test is commonly used alongside other markers, such as erythrocyte sedimentation rate (ESR), to provide a clearer picture of a patient's health status.