TL;DR
Cats hide when they're stressed, overstimulated, or unwell. A cat who hides but comes out to eat, drink, and use the litter box is coping. A cat who hides and stops eating for more than 24 hours needs a vet.
Why hiding is normal
Cats are both predator and prey. Hiding is how they self-regulate — after a stressful event, a new person in the house, or just a loud afternoon. A cat who has a favorite hiding spot is a cat who feels safe enough to have one.
What to watch
The signs that hiding is coping, not a crisis: they still come out to eat, still use the litter box, and still respond to their name (even if they don't come). Track those three things and you'll spot a real change fast.
When to call the vet
A cat who stops eating for 24 hours, stops using the litter box, or hides in a way that's new for them — especially a normally social cat — needs a vet visit. Cats are extraordinary at hiding pain, and 'hiding more' is often the first visible sign of illness.
