The human body maintains a relatively stable internal temperature, a process known as thermoregulation. While often cited as 98.6°F (37°C), a person’s normal body temperature can vary. For most adults, a typical oral temperature ranges between 97°F and 99°F. Children generally have a slightly wider normal range, from 95.9°F to 99.5°F when measured orally. Minor fluctuations throughout the day are common and do not necessarily indicate illness.
Understanding 99.8 and Fever
A temperature of 99.8°F falls within a range that can be ambiguous, as it is slightly elevated but often not considered a true fever on its own. Healthcare providers typically define a fever as an oral temperature of 100.4°F (38°C) or higher. Some sources consider a temperature between 99.5°F and 100.3°F (37.5°C and 37.9°C) to be a low-grade fever. A single reading of 99.8°F might simply be a normal variation for an individual or a temporary elevation due to non-illness factors.
Common Influences on Body Temperature
Several factors unrelated to illness can cause a person’s body temperature to fluctuate and potentially reach 99.8°F. Body temperature naturally varies throughout the day, typically being lowest in the early morning and highest in the late afternoon or evening. Physical activity, even moderate exertion, generates heat and can temporarily raise body temperature. Hormonal changes, such as those occurring during ovulation in women, can also lead to a slight increase in basal body temperature. Eating a meal can cause a temporary rise in temperature.
When to Seek Medical Advice
While a temperature of 99.8°F may not always be concerning, specific accompanying symptoms or circumstances warrant medical attention.
If the elevated temperature persists for more than three days.
For infants younger than three months, any rectal temperature of 100.4°F (38°C) or higher requires immediate medical evaluation, as even a low fever can indicate a serious infection in this age group.
If the temperature is accompanied by concerning symptoms such as difficulty breathing, severe headache, stiff neck, rash, confusion, persistent vomiting, or severe pain.
Individuals with compromised immune systems or underlying health conditions should also consult a doctor for any persistent or unusual temperature elevation.