What actually happens during a fever that makes you shiver and ache?

[Thomas_M]

I've been reading about how the body regulates its core temperature, but I'm confused about what actually happens during a fever. My understanding is the hypothalamus resets the body's thermostat, but I don't really get why that causes such intense chills and muscle aches before the temperature rises.

[Nathan_G]

That chills then heat swing is the weirdest part. When the body decides to raise heat, the skin tightens and you start to shiver, you feel cold even as your cheeks flush. It passes once the body catches up.

[Jason_R]

I once had a fever and started out freezing under blankets, then suddenly felt overheated and wiped out. The muscle aches were brutal, like every movement pulled. It was as if the body was using up all its energy to fight something I couldn’t see.

[MatthewT]

A nurse friend explained it this way: the hypothalamus is the body's thermostat. The immune signals wake it up and raise the set point so your core temp climbs. You shiver to generate heat, and the ache comes from the effort and staying still and dehydrated.

[Thomas_H]

Is the real problem the infection or the fever itself, though? I keep wondering if focusing on the temp misses what’s actually going on.