1. R50 Fever of other and unknown origin


    • chills without fever (R68.83)
    • febrile convulsions (R56.0-)
    • fever of unknown origin during labor (O75.2)
    • fever of unknown origin in newborn (P81.9)
    • hypothermia due to illness (R68.0)
    • malignant hyperthermia due to anesthesia (T88.3)
    • puerperal pyrexia NOS (O86.4)
    1. R50.2 Drug induced fever

    2. R50.8 Other specified fever

      1. R50.81 Fever presenting with conditions classified elsewhere

      2. R50.82 Postprocedural fever

      3. R50.83 Postvaccination fever

        Inclusion term(s):

        • Postimmunization fever
      4. R50.84 Febrile nonhemolytic transfusion reaction

        Inclusion term(s):

        • FNHTR
        • Posttransfusion fever
    3. R50.9 Fever, unspecified

      Inclusion term(s):

      • Fever NOS
      • Fever of unknown origin [FUO]
      • Fever with chills
      • Fever with rigors
      • Hyperpyrexia NOS
      • Persistent fever
      • Pyrexia NOS
Abbreviations used here:

NEC Not elsewhere classifiable
This abbreviation in the Tabular List represents “other specified”. When a specific code is not available for a condition, the Tabular List includes an NEC entry under a code to identify the code as the “other specified” code.

NOS Not otherwise specified
This abbreviation is the equivalent of unspecified.