R50: Fever of other and unknown origin

R50.9: Fever, unspecified

Normal body temperature ranges between 36 and 37 degrees Celsius. A body temperature over 38 degrees Celsius means you have a fever. Fever can have a number of causes. You can have a fever, for example, if you are infected with pathogens. Various conditions can also cause fever. You may also have chills and feel unwell.