From the Guidelines
A fever is generally considered to be a body temperature of 100.4°F (38°C) or higher, as defined by the most recent guidelines from the Society of Critical Care Medicine and the Infectious Diseases Society of America 1.
Definition of Fever
The definition of fever can vary depending on the context and population, but a temperature of 100.4°F (38°C) or higher is a commonly accepted threshold.
- Normal body temperature typically ranges from 97°F (36.1°C) to 99°F (37.2°C), with 98.6°F (37°C) often cited as the average.
- Fever thresholds may vary slightly depending on age, with children sometimes having different parameters, and the method of measurement also matters - oral, rectal, ear, or forehead temperatures can differ by small amounts.
Clinical Considerations
Fevers are the body's natural defense mechanism against infection, as many pathogens cannot survive at higher temperatures.
- While low-grade fevers (up to 102°F or 38.9°C) often don't require treatment unless uncomfortable, higher temperatures may warrant fever reducers like acetaminophen (Tylenol) at 325-650mg every 4-6 hours or ibuprofen (Advil, Motrin) at 200-400mg every 6-8 hours.
- If a fever exceeds 103°F (39.4°C) in adults, persists beyond three days, or is accompanied by severe symptoms like difficulty breathing, confusion, or stiff neck, medical attention should be sought promptly, as indicated by the guidelines from the Society of Critical Care Medicine and the Infectious Diseases Society of America 1.
Special Populations
It's worth noting that some populations, such as the elderly or those with certain medical conditions, may have different definitions of fever or require more prompt medical attention, as outlined in guidelines from the Infectious Diseases Society of America 1.
- For example, in older adult residents of long-term care facilities, fever is defined as a single oral temperature ≥100°F (37.8°C) or repeated oral temperatures ≥99°F (37.2°C) or rectal temperatures ≥99.5°F (37.5°C) 1.
- In infants and children, the definition of fever and the approach to management may also vary depending on age and other factors, as discussed in guidelines from the American College of Emergency Physicians 1.
From the Research
Definition of Fever
- Fever is defined as an elevated body temperature, with normal body temperature typically considered to be around 37°C (98.6°F) 2.
- However, the exact temperature that constitutes a fever can vary, with some studies defining fever as an oral or rectal temperature of 39°C to 40.5°C (102.2°F to 104.9°F) 3.
- Other studies define fever as an axillary temperature of 38.5°C (101.3°F) or higher 4.
Temperature Ranges for Fever
- Normal body temperature: around 37°C (98.6°F) 2.
- Fever:
- Hypothermia: temperature of less than 35.6°C (96.1°F) 3.