If her fontenal is still open, you can tell dehydration by a sunken fontenelle.  If not and she is little, skin won't spring back when pinched beside her belly button.

Hope this helps.

Jodi

I would take her to the doctor if she isn't drinking or peeing. If you can get her to eat iceblocks that will help a lot - especially if you can get her to eat Hydralyte ones. Try and get fluids into her anyway you can but if she won't have them go to the doctor.

If she is unusually lethargic, if her skin is losing elasticity, or looking really dry, or if nothing been peed tomorrow morning, I would take her to the doctor. Try and get her to eat an iceblock if that might help.

If this is the same by morning take her to a doctor. To check if she's dehydrated, look in her mouth - do her lips look dry? Does it look dry under her tongue (ie, no saliva)? If so maybe get her checked out asap. If she's not eating much, she may just be coming down with a bit of a bug. Give her plenty of water. If she starts screaming in pain get her to a doctor, otherwise see how she goes overnight.