Why is 37°C considered the threshold to say you have fever?

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Why is 37°C considered the threshold to say you have fever?

In: Biology

5 Answers

Anonymous 0 Comments

A lot of people saying its arbitrary…
It’s not.
This is a bit above ELIA5, but anyway…
Like all physiological references ranges, they’re based on healthy individuals.
You measure lots of and lots healthy individuals for something e.g. how much haemoglobin they have in their blood. A very few people will have a low haemoglobin, and that’s normal for them. The vast majority will have a haemoglobin thats middle of the pack. And a very few will have a naturally very high haemoglobin – and that’s normal for then.
We then dictate the “normal range” as being the range that the middle ~90% of people (the vast majority) sit inside. So at the extreme highs and low, we know that up to 5% of people have those levels naturally, but the vast majority of people who we test suspecting that their haemoglobin will be abnormal who return results that are very high/low have extreme results because there is something wrong with them causing this result thats so far off the average.
(Google “Normal Distribution”for nice pictures of this)
Replies here have been debating “well in my job as an x, its not a temperature unless its over y”. This is because individual laboratories and equipment use slightly different methods, and tests and equipment has different error margins etc etc. So your “normal ranges” will often vary slightly from place to place.
In addition to this, different diagnostic pathways kick in at different disease severities. We may treat a temp of 38.5 with paracetamol (tylenol…) because the risk of being seriously ill is low and youre more likely to come to harm because of aggressive treatment than to benefit.

But we know a temperature of 40 is much more serious and you’re more likely to come to harm if we do nothing. This is why sometimes healthcare workers give different amounts of shits at different disease (or in this case, fevers) severeties.

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