When a dog is dehydrated the dog will have reduced urine output, increased thirst, have a dry nose and dry mouth, have sunken eyes, dry and sticky gums and a loss of skin elasticity, which is when the skin does not spring back quickly when the skin is pinched.
Other signs of a dog being dehydrated are lethargy and weakness, panting excessively, decreased appetite, confusion or disorientation, wobbly gait, hiding in cool places, reluctance to play or exercise, increased sensitivity to noise or touch and an increased heart rate, rapid breathing, thick and sticky saliva and constipation.
To rehydrate your dog, offer the dog some fresh water frequently.
You can also flavor the dogs water with some broth that is low in sodium or even give the dog some ice chips.
Also adding some wet food to the dogs diet or mixing some water in some dry dog food can also help to rehydrate the dog.
If the dehydration is really severe the dog may need to see a vet and may need IV hydration to restore hydration and electrolytes.
Dogs that have underlying health conditions such as kidney disease, Cushing's disease or diabetes may drink more water.
Dogs should have access to fresh water at all times so they can drink when they are thirsty.
A dog can go 72 hours without water, but the effects of dehydration in the dog will become apparent after the first 24 hours without water.