Interpretation of digital thermometer readings

[chhow]

Can anyone link me to an authoritative source on how to interpret armpit readings from a digital thermometer?

Our digital thermometer always measures low - it gives readings of 36ish C (oral) for my husband and I when well, and 35ish C (armpit) for baby when he's well. Normal human body temperature is supposed to be 37 C.

I think I remember reading somewhere that this type of thermometer reading is typically a bit lower than whatever the gold standard is. But now I can't find the source for what I read.

Baby currently has a temperature following his 5 month vaccinations, and this morning the thermometer read 37.9. I'm not sure if I should interpret that as borderline fever (they say fever starts at 38 C), or if I should compare it to the thermometer's "normal" of 35 and panic because it's almost 3 degrees above "normal". That would imply a temp of almost 40 C if I correct for bias in the thermometer, which seems implausible. Baby is unhappy but he's not 40 degrees unhappy.

Glossary for Americans
35 C = 95 F
36 C = 96.8 F
37 C = 98.6 F
38 C = 100.4 F
39 C = 102.2 F
40 C = 104 F

 

[bastionhd]

@chhow There should be a booklet with your thermometer stating the normal temperature ranges for different places of measurement (oral, rectal, underarm). Contrary to popular belief, 37°C is not the normal body temperature for an adult, it’s more somewhere between 35,6° and 36,8°.

 

[kickthichphattiren689]

@bastionhd

Contrary to popular belief, 37°C is not the normal body temperature for an adult, it’s more somewhere between 35,6° and 36,8°.

Do you have a source for this? 36.5–37.5 °C (97.7–99.5 °F) is a typically reported range for normal body temperature according to Wikipedia. 35.6° sounds awfully low.

The exact range isn't really important for an individual to know, I suppose. It's better to know what one's own nominal temperature is.

 

[bastionhd]

@kickthichphattiren689 https://www.nationalgeographic.co.u...human-body-temperature-and-is-it-cooling-down

I know it’s not a scientific source but it was the fastest I could find that points at the study I was thinking about. I’ll admit the range I gave wasn’t accurate, but my point was mostly that the average is lower than we were thought to believe.

All I know is I spent a lot of time explaining to people in the beginning of the pandemic that they didn’t need to buy a new thermometer because the one they had at home only said 35.7°C so it must be broken (there was a shortage in thermometers back then).

 

[katrina2017]

@chhow Ours is the Vicks rapid read that came with this instruction - A rectal temperature is generally 0.5 Degrees Celsius/1.0Fahrenheit higher and an underarm (axillary) temperature will be 0.5 Degrees Celsius/1.0Fahrenheit lower.

We measure underarm for our baby so we add 0.5c to the read. If you've measured that 37.9 underarm I suggest it is over 38c so there is a fever.

 

[fromtheearth]

@katrina2017 I second adding 0.5º C to armpit temperature for the “right temperature”. It was explained today by our midwife.

 

[kitty88]

@katrina2017 This is what our pediatrician said, and it rings close to true. On Sunday, my baby had a fever. It was 100.94 F at the armpit at home, and was 101.4 F rectally an hour later at the doctor’s office. (FWIW, we also used a forehead thermometer, which read 98.4 F minutes before the armpit reading. The forehead thermometer is going out with the trash today.)

 

[lisad65]

@chhow Certain thermometer types are less reliable/accurate (such as non-contact infrared thermometers according to the CPS), and different methods (locations) of taking the temperature are more or less accurate for different age groups.

This table is from the Canadian Pediatric Society (CPS):
Method / Normal temperature range
- Rectum / 36.6°C to 37.9°C (97.9°F to 100.2°F)
- Mouth / 35.5°C to 37.5°C (95.9°F to 99.5°F)
- Armpit / 36.5°C to 37.5°C (97.8°F to 99.5°F)
- Ear / 35.8°C to 37.9°C (96.4°F to 100.2°F)

Here is the source with additional information and tips on temperature taking.

 

[lightdreamer]

@lisad65

36°C is equivalent to 97°F, which is 309K.​

[sup]I'm a bot that converts temperature between two units humans can understand, then convert it to Kelvin for bots and physicists to understand[/sup]

 

[chhow]

@lisad65 Thank you, this is exactly what I was hoping to find!