What is a normal body temperature, and what counts as fever?
Normal body temperature is a range, not 37.0. Most adults run 36.1 to 37.2 C (97 to 99 F). It is lower in the morning, higher by evening, and slightly lower in older age. Modern averages run cooler than the 19th century textbook number.
Fever formally starts at 38.0 C (100.4 F). How you measure matters: ear and forehead read differently from mouth, and armpits read lowest.
Know your own baseline by measuring when well; a person who runs 36.2 is really feverish at 37.8. In the very old, serious infection can arrive with barely any fever at all.
See a doctor promptly if
- 104 F (40 C) or higher in an adult needs a doctor today; 105 F (40.6 C) is an emergency
- Fever with a stiff neck, confusion, trouble breathing, or a rash that does not fade under pressure
- In adults over 65 and people on chemotherapy or immune-suppressing medicines, even a small fever deserves a same-day call
- A temperature below 95 F (35 C) in an adult, especially with shivering, drowsiness or confusion, needs urgent care
- Any fever that lasts more than three days, or returns after settling, needs a doctor rather than another tablet
- Fever with severe headache, chest pain, a hot swollen limb, or pain and burning on passing urine with back pain
Is this temperature a fever?
| Result | In short | What it means |
|---|---|---|
| 36.0 to 36.4 C (96.8 to 97.5 F) | Normal, low side | The low end of ordinary. Common first thing in the morning and in older adults. Not a sign of anything on its own. |
| 36.5 to 37.2 C (97.7 to 99.0 F) | Normal | Ordinary at any hour. Most people sit at the top of this band in the late afternoon and the bottom of it at dawn. |
| 37.3 to 37.5 C (99.1 to 99.5 F) | Not a fever | Above your usual, under the line. Recheck in an hour, sitting quietly, away from a hot drink, a warm room or exercise. |
| 37.6 to 37.9 C (99.7 to 100.2 F) | Low-grade | Not a fever officially. In someone who feels unwell it is the start of one, and it is worth rechecking rather than dismissing. |
| 38.0 C (100.4 F) | Fever | This is the line in every guideline. In a baby under three months it is an emergency on its own, whatever else seems fine. |
| 38.1 to 38.9 C (100.6 to 102.0 F) | Fever | A clear fever. How long it lasts and what comes with it matter far more than the number itself. |
| 39.0 to 39.9 C (102.2 to 103.8 F) | High fever | Treat the discomfort, keep fluids going, and see a doctor the same day if it holds for more than a day or two. |
| 40.0 C (104.0 F) and above | See a doctor now | Same-day care in an adult. With confusion, a stiff neck, a rash that does not fade under pressure, or trouble breathing, it is an emergency. |
Where you measure changes the number: forehead and armpit read low, rectal reads high. Compare like with like across the day. Check it against the guidelines.
Try the fever check30 seconds, free, nothing to installWhat your reading means by the way it was taken, because an ear, a forehead and a mouth do not agree.
Look up another result
A result is rarely the only one on the page. Each of these gives the bands, in both unit systems, and what happens next.
- PSA result7 bands
- Reading after a meal5 bands
- Resting heart rate7 bands
- Sodium result6 bands
- Taking them together, safely6 bands
- Testosterone result4 bands
- The five criteria, and the threshold for each5 bands
- The five numbers that decide what a plan costs you6 bands
- The stages, and what they do and do not tell you6 bands
- The supplements that turn up in liver injury6 bands
- TSH number7 bands
- Typical overnight HRV by age6 bands
- Uric acid result5 bands
- Vitamin D result6 bands
Answered by the AskDoc Medical Team · Medically reviewed under our Medical Director, MBBS · How we review
If you are buying a thermometer
A basic digital stick thermometer is accurate and costs a few dollars. Forehead scanners are fine for quick checks on children; ear thermometers need good technique to read true.
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