Which of the following temperatures is considered a fever in adults?

A temperature above 100.4°F (38°C) is considered a fever in adults because it indicates that the body is responding to an infection or illness. The normal body temperature for adults typically ranges from about 97°F to 98.6°F (36.1°C to 37°C), but this can vary slightly depending on the individual and the time of day. When the temperature exceeds 100.4°F, it signifies that there may be an underlying issue that requires medical attention, especially if the fever persists or is accompanied by other symptoms. This threshold is widely used in clinical settings to identify fever and prompt further evaluation and intervention if necessary.

The other options do not correctly define fever. A temperature below 98.6°F is considered within normal limits or possibly indicative of hypothermia, while a range between 99.0°F and 100.4°F is considered elevated but not definitively a fever. Although a temperature above 101°F is indeed higher and may be concerning, it is still correct to state that the threshold for identifying a fever starts at 100.4°F.