Temperature Range Definitions in Clinical Practice

Normal Body Temperature (Normothermia)

The American College of Critical Care Medicine defines normal body temperature as <38.0°C (100.4°F) for clinical purposes, which is used by the CDC for hospital-acquired infection surveillance 1
Special populations, such as elderly patients (>65 years) in long-term care, have adjusted thresholds, with normal defined as oral temperature <37.8°C (100.0°F) or rectal <37.5°C (99.5°F) 1

The Society of Critical Care Medicine (SCCM) and the Infectious Diseases Society of America (IDSA) define high-grade fever as ≥38.3°C (≥101°F), which is the threshold used in ICU patients and in neutropenic patients receiving chemotherapy 1
Temperatures >40°C (104°F) require urgent investigation and treatment of the underlying cause, according to clinical guidelines 2

Controlled normothermia (36.0-37.5°C) should be actively maintained in traumatic brain injury patients as part of Tier 1 and Tier 2 intracranial pressure management, with neurogenic fever >37.5°C treated promptly regardless of ICP level, as recommended by critical care guidelines 3
The absence of fever in infected patients paradoxically indicates worse prognosis, so these recommendations apply to suspected infection regardless of temperature elevation, according to the American College of Critical Care Medicine 1