Fever. A fever is typically considered problematic once it goes over 100.4 degrees Fahrenheit. High levels of white blood cells are linked to fevers because both issues are signs of an immune system response. When the immune system senses a threat, such as a bacteria or virus that causes an illness, it raises the temperature of the body to make it less hospitable for infectious growth and sends out more white blood cells to eliminate the invader. Therefore, fevers usually mean that white blood cell counts are high because the body currently has an elevated immune response. This often happens when a person is fighting off an illness, but fevers and high white blood cell counts can also occur when a person is suffering from an autoimmune disorder that causes an overactive immune system.
