The normal temperature of the human body ranges from 97°F to 99°F (36.1°C to 37.2°C), with small daily fluctuations that usually do not exceed 1°F (0.6°C). Body temperature tends to be lower in the morning, rises during the day, and reaches its highest point in the early evening. On average, a normal temperature is around 97.7°F (36.5°C) in adults, babies, and children.
A temperature between 99°F and 100.4°F (38°C) is considered a low-grade fever, meaning there is a slight increase that generally does not cause any major effects on the body. Certain situations can naturally raise the body’s normal temperature without indicating illness. For example, during the first trimester of pregnancy or after ovulation, it is normal for body temperature to rise by up to 1°C. This occurs because the brain’s temperature regulation center adjusts heat production and loss to maintain balance between the body and the environment.
A true fever occurs when body temperature rises above 100.4°F (38°C). At this level, symptoms such as chills, sweating, and general discomfort may appear. When the temperature reaches around 102.2°F (39°C), it can cause confusion and delirium, and temperatures above 104°F (40°C) may trigger seizures.
Immediate medical attention is recommended if a fever is accompanied by skin rashes, behavioral changes, confusion, seizures, difficulty breathing, persistent vomiting, or severe headache. A fever in babies under 3 months of age should always be treated as an emergency.
Fever is the body’s natural defense against infection, as the higher temperature helps slow the growth of microorganisms and makes them less active. Fever reducers (antipyretics) like acetaminophen should only be used if the temperature reaches 100.4°F (38°C) or higher and causes discomfort. Overuse of these medications can be harmful and may prolong the illness or increase the risk of complications.