The other thing you might find, when looking you underneath their lip, that their gums may look a bit dry, a bit sticky, a bit tacky and that is another clue that they may be dehydrated. If you are used to how your dog’s gums look like and how your dog’s coat looks like, then you will notice if there is a change and that is important to know what is normal so you can then pick up what is abnormal and relay that to the vet, if you are phoning them with a concern.
If they are dehydrated and it is true dehydration, you need to correct that quite quickly. If your dog is, or cat is still well in themselves, offer them more water. Try and encourage them to drink more. Might be if they are still eating, you can just add some water into their food and get them to drink that way without them having to lap from a bowl.
If they are off their food or they are getting more dehydrated, you really need to be seen by a vet quite urgently so that they can correct that, either with intravenous fluids or subcutaneous fluids, which is where we inject fluids underneath the skin that then just disperse around the body. The other thing that happens in dehydration is you get a drop in electrolytes because fluids carry those important electrolytes that make all your organs and all your cells work. So once you are at the vet’s, they will probably supplement with those electrolytes in the fluids that they are giving your animal as well.