When blood tests are performed for fever, in general, blood sampling refers to checking inflammatory indicators such as routine blood tests, C-reactive protein and calcitoninogen, but more often pathogenic tests of blood are performed, including antigen antibody tests and bacterial cultures, to clarify whether the fever is due to bacteria, fungi or viruses. When examining the blood, the main purpose is to look for any blood system disorders. It is also important to check for elevated white blood cells or neutrophils. The presence of elevated values of white blood cells or neutrophils often indicates the presence of a bacterial infection.