Nonfebrile

Nonfebrile is a medical adjective used to describe the absence of fever in a patient. It characterizes a clinical state in which body temperature remains below the threshold typically used to define fever, and it is often applied in descriptions of illnesses, examinations, or responses to treatment where fever is not present.

Fever is commonly defined as a body temperature at or above about 38.0°C (100.4°F) when measured by standard methods (oral, tympanic, rectal). Normal basal temperatures typically range from roughly 36.5–37.5°C (97.7–99.5°F) and can vary by individual, time of day, and measurement site. Nonfebrile means the reading stays below the febrile threshold during assessment.

Nonfebrile presentations occur in a variety of conditions, including localized infections without systemic fever, inflammatory diseases, heat exposure, or noninfectious causes of illness such as injury or medication effects. In children and older adults, fever patterns can differ from adults, and afebrile status does not always imply absence of disease.

Absence of fever does not exclude illness. Some patients, particularly the elderly, neonates, or immunocompromised individuals, may be afebrile even in the presence of infection. Fever can also be transient or suppressed by antipyretic medications, and measurement technique or timing can influence the recorded temperature.

Related terms include afebrile and normothermic; nonfebrile is used alongside these in clinical descriptions.