A fever is a temporary rise in body temperature, usually caused by an infection. For most adults, a fever is when the body temperature is at or above 100.4°F (38°C) . However, normal body temperature can vary between individuals and throughout the day, and it can range between 97°F (36.1°C) and 99°F (37.2°C) or more. Healthcare providers most often say a fever temperature is 100.4°F (38°C) when measured orally (by mouth) .
There are different levels of fever severity, including:
- Low-grade: 99.1 to 100.4°F (37.3 to 38.0°C)
- Moderate-grade: 100.6 to 102.2°F (38.1 to 39.0°C)
- High-grade: 102.4 to 105.8°F (39.1 to 41°C)
In adults, fevers less than 103°F (39.4°C) are typically not dangerous and are not a cause for concern. However, if the fever rises above that level, it is recommended to call a healthcare provider for treatment. Seek immediate medical attention if any of the following signs or symptoms accompany a fever:
- Severe headache
- Rash
- Unusual sensitivity to bright light
- Stiff neck and pain when you bend your head forward
- Mental confusion, strange behavior, or altered speech
- Persistent vomiting
- Difficulty breathing or chest pain
- Abdominal pain
- Pain when urinating
- Convulsions or seizures
