A high C-reactive protein level in a child may be due to strenuous exercise, an infectious disease or an autoimmune disease. 1. Strenuous exercise: If a child exercises strenuously before taking a C-reactive protein test, it is very likely that the test results will be affected and the value will be elevated. 2. Infectious diseases: Bacterial infections in a child’s body can also cause C-reactive protein to rise. 3. Autoimmune diseases: High C-reactive protein in children may also indicate autoimmune diseases such as lupus erythematosus or Kawasaki disease, and C-reactive protein will increase significantly when the patient is in the middle of an attack. When C-reactive protein is elevated in children, further tests should be ordered to clarify the situation.