What are the common misunderstandings about taking your temperature?
This answer is a draft. It stays unpublished until legal review and source verification are complete.
Since 2020, people all over the world have taken their temperature far more often, and questions like "how many minutes under the arm?" and "are no-touch forehead thermometers accurate?" have surged. In Japan, thermometers are regulated as medical devices with their own standards, and there is a set way of measuring.
Sites and device types
| Site / type | Features | Guide |
|---|---|---|
| Underarm (axillary), direct-reading | Standard in Japanese homes. About 10 minutes for the armpit temperature to stabilise | Often around 36.0–37.0°C (96.8–98.6°F) |
| Underarm, predictive | Predicts from the rise curve. About 15–30 seconds. Many models switch to direct reading if you keep it in place after the display | As above |
| Mouth (under the tongue) | About 0.2–0.5°C higher than underarm. Standard in Europe and North America | — |
| Ear (tympanic) | Fast, but error from the angle of the ear canal and from earwax | — |
| Forehead, non-contact | Infrared from the skin surface. Varies with outside air, sweat and make-up; for screening | Large individual variation |
| Rectal | Closest to core temperature. Used for infants | About 0.5°C higher than underarm |
- Household thermometers are "controlled medical devices" under the Pharmaceuticals and Medical Devices Act (Japan's drugs and devices law), certified to standards such as JIS T 1140 (electronic clinical thermometers).
- Body temperature has a daily rhythm (about 0.5–1°C): lower in the morning, higher in the evening. It reads high right after a meal, exercise or a bath. The basic rule is to compare at the same time, at the same site, with the same thermometer.
[Verify] Check the JIS standard number and the medical-device classification against MHLW and Japan Federation of Medical Devices Associations material, and the site differences against standard physiology references.
Misunderstanding 1｜Normal is 36.5°C, and anything else is abnormal
Normal temperature ranges from the 35s to around 37°C depending on the person. Know your own baseline first (measure morning, noon and evening for a few days). The usual guide figure for "fever" under Japan's Infectious Diseases Control Act is 37.5°C (99.5°F) or above.
Misunderstanding 2｜The no-touch forehead type is the most accurate
It is the fastest and the least accurate. Outside air, sweat or a bath just before can shift it by several degrees. It suits screening, but to judge how you are, measure again under the arm or similar.
Misunderstanding 3｜With a predictive thermometer, the beep means you are done
The beep gives a predicted value. To know precisely, leave it in place for 10 minutes and read the direct measurement (on compatible models).
Misunderstanding 4｜Anywhere in the armpit will do
Place the tip in the centre (the hollow) of the armpit at about 30 degrees from below, and press the arm against the body. Wipe away sweat. Off-centre, the reading comes out low.
Misunderstanding 5｜Right after exercise or a bath is the same
It reads high for about 30 minutes. Rest first, then measure. Your temperature straight after waking is the most stable baseline for comparison.
---
Sources
- Ministry of Health, Labour and Welfare, "Classification and regulation of medical devices" [医療機器の分類と規制] (thermometers are controlled medical devices)
https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/iyakuhin/index.html
- Japanese Industrial Standards Committee (JISC), JIS T 1140 "Electronic clinical thermometers" [電子体温計]
https://www.jisc.go.jp/
- Ministry of Health, Labour and Welfare, COVID-19 Q&A, "Definition of fever under the Infectious Diseases Control Act (37.5°C or above)" [感染症法に基づく発熱の定義（37.5℃以上）]
https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/dengue_fever_qa_00001.html
⚠️ Editorial note: the source URLs above were identified by search. Our working environment cannot reach go.jp domains, so the contents have not been checked against the text. Verify every source before publication and record who checked it and when.
About this article
What we share here are ideas and everyday practices passed down among people living in Japan, together with general information drawn from public sources. They are not official recommendations, and they are not professional instruction. Practices vary between households and regions.
This is general information. Results vary from person to person and depend on your own conditions and surroundings.
Please decide for yourself, using your own judgement, whether any of this suits your situation. We cannot accept responsibility for any damage, loss or injury arising from following this article.
This article is not meant to diagnose or manage any specific medical condition. If you are worried about your health, see a doctor rather than relying on your own judgement.
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