Under arm temperatures?

[Sodabread]

When taking temperature with an under arm digital thermometer, the gp said add on .5 degrees. Do people actually do that?

My 15 week old has a temperature of 37.3/5, and if I add on the .5 it makes it 38, which is a temperature I ought to be alert to, otherwise it's just a slightly warm temperature. She is off colour and full of cold, but still feeding, wet nappies etc...I'm not sure how much I should be concerned. Gp saw her yesterday and said she was ok, but didn't take her temperature, but health visitor saw her today and said keep a close eye on her...

No I'm a children's nurse and have never done that and we use underarm thermometers.

Well I have an in the ear temperature however ds gets ear infections which can distort the reading, so I use it under his arm, or under his tongue or on his forehead, or all three depending. He thinks it's quite funny.

I would say the hottest temperature is under the tongue, followed by in his ears (if they're fine) then under his arm or forehead. I think there's about a 0.5 variation between ears and under arm typically, so that's why you would be worried sooner with a high under arm.
It's not consistent though, so if he's been tucked up in bed, under the arm may be hotter. Running round with nothing on may be cooler.

I go by feel most of the time, I only take temperature to get a reference if it's getting hotter or colder, so it matters less there.

Take a look at this website - about half way down the page there is a green yellow and red table that gives you some guidelines as to when to worry. patient.info/doctor/ill-and-feverish-child

What I would say is go with your instinct too. Absolute numbers matter less if your child is otherwise reasonably alert and feeding vs if they are listless, pale and not with it at all. If in doubt get a medical professional to have a look.