Your dog’s skin will lose elasticity as it loses it’s moisture. Younger, fatter dogs will have more elasticity than older, thinner dogs. Because of this, it is important to know what your dog’s skin looks and feels like on a normal basis. When you pinch the skin of your dogs back between your thumb and forefinger, it should return to normal immediately. As the tissue loses it’s moisture, it will move back slower, and in some extreme cases, it won’t move back at all.
Another way to check if your dog is dehydrated would be to pull up your dog’s lip and look at their gums. Put your index finger firmly against the gums so they appear white. When you remove your finger, take a look at how quickly the blood returns to the gums. They will become pink in that area again. This is called capillary refill time. If you do this when your dog is completely hydrated, you will have a basis to compare with. The gums of a healthy, hydrated dog will refill immediately, while the gums of a dehydrated dog could take 3 seconds or so to return to their normal state.
If you are unsure of your pets condition be sure to contact your Veterinarian, as soon as possible...