From the Guidelines
A fever is generally defined as a body temperature of 38°C (100.4°F) or higher. This definition is based on the most recent and highest quality study available, which emphasizes the importance of accurate temperature measurement in the diagnosis of fever 1. Low-grade fevers range from 38°C to 38.9°C, moderate fevers from 39°C to 39.9°C, and high fevers are 40°C and above. Fever is the body's natural defense mechanism against infection, as many pathogens cannot survive at higher temperatures.
Some key points to consider when evaluating fever include:
- The reliability of temperature measurements, with rectal temperatures being the most accurate 1
- The definition of fever may vary depending on the population being studied, such as neutropenic patients or children 1
- Fever can be a symptom of a serious underlying infection, and it is essential to monitor symptoms and seek medical attention if necessary
While fever itself is not typically dangerous until it reaches about 41°C (105.8°F), it's crucial to monitor symptoms and seek medical attention for persistent fevers above 39.4°C (103°F), fevers lasting more than three days, or fevers accompanied by severe symptoms. For fever management, acetaminophen (paracetamol) or ibuprofen can be used following package dosing instructions, along with staying hydrated and resting. Remember that fever is a symptom, not a disease itself, and treating the underlying cause is essential. The most recent study on the topic, published in 2016, supports this definition and approach to fever management 1.
From the Research
Definition of Fever
- Fever is defined as a core body temperature of >38.3 degrees C 2, 3, 4
- This definition is widely accepted and used in clinical practice to diagnose and manage fever in patients
Temperature Range for Fever
- A temperature range of >38.3 degrees C to 39.5 degrees C is commonly associated with fever 2, 3, 4
- Temperatures above 39.5 degrees C may have negative sequelae and require prompt treatment 4
- Temperatures below 38.3 degrees C are generally not considered feverish, but may still be associated with infection or other underlying conditions 5
Clinical Significance of Fever
- Fever is a complex physiological response involving the innate immune system and should not be characterized merely as a temperature above a certain threshold 5
- Fever can be caused by both infectious and non-infectious causes, and its development in critically ill patients is associated with an increased risk for death 2, 3
- The management of fever is crucial, and a structured approach is required to correctly diagnose and treat fever in critically ill patients 2, 3, 4