what temp is considered a fever
A fever is usually considered a body temperature of 100.4°F (38°C) or higher, but the exact cutoff depends on how and where you measure it.
Quick Scoop
Normal vs fever
- Normal adult body temperature averages around 98.6°F (37°C), but healthy ranges are roughly 97–99°F (36.1–37.2°C). Values above this range may signal a developing fever.
- Many doctors use 100.4°F (38°C) as the practical point where “this is a fever ” rather than just “a little warm.”
By thermometer type
Most major medical sources give these common fever thresholds:
- Oral (mouth):
- Fever: about 100–100.4°F (37.8–38°C) or higher.
- Rectal / ear / forehead (temporal):
- Fever: 100.4°F (38°C) or higher.
- Armpit (axillary):
- Fever: around 99–99.5°F (37.2–37.5°C) or higher.
In plain terms: if a reliable thermometer reads around 100.4°F (38°C) or more, most doctors would call that a fever.
When it’s more serious
Get urgent medical help (or call emergency services) if:
- The person is very hard to wake, confused, or has trouble breathing.
- There’s a stiff neck, severe headache, chest pain, or a seizure.
- A baby under 3 months has a rectal temperature of 100.4°F (38°C) or higher.
- Fever lasts more than a few days or keeps climbing despite fluids and over‑the‑counter medicine.
Quick numbered recap
- Under ~99°F (37.2°C): Often normal for adults, depending on the person and time of day.
- Around 99–100.3°F (37.2–37.9°C): Low‑grade or “slightly elevated,” may be early infection or normal variation.
- 100.4°F (38°C) and above: Generally considered a true fever.
- 102–104°F (38.9–40°C): Higher fever; watch symptoms closely and consider medical advice, especially in children, older adults, or those with health issues.
Bottom note: This is general information, not a diagnosis. If you or someone else feels very unwell or you’re unsure what to do about a fever, contact a health professional.