What dehydration means
A dog is dehydrated when their body loses more water than it takes in. Water carries nutrients, cools the body through panting, cushions joints and keeps the organs working. Even mild dehydration can make a dog feel tired and unwell. Severe dehydration can damage the kidneys and other organs, and can be life-threatening.
Dogs lose water all the time by breathing, panting, peeing and pooing. Most healthy dogs replace it by drinking. Problems start when losses go up (heat, exercise, vomiting, diarrhoea) or when they can't or won't drink enough.
Signs to watch for
| Sign | What it looks like |
|---|---|
| Dry or sticky gums | Gums feel tacky or dry instead of wet and slippery |
| Thick saliva | Stringy, ropey drool instead of thin and watery |
| Tiredness | Less interest in walks, play or food; slow to get up |
| Sunken eyes | Eyes look duller and set deeper than usual |
| Loss of skin elasticity | Skin over the shoulders is slow to fall back when lifted |
| Slow capillary refill | Gum colour is slow to return after pressing |
| Dark urine | Darker yellow, stronger smell, or peeing less than usual |
| Panting | Heavy panting, especially in the heat or at rest |
Dogs don't always show every sign. A tired, quiet dog with sticky gums on a hot day already deserves your attention.
Two quick checks you can do at home
The skin tent test
Gently pinch and lift a fold of loose skin over your dog's shoulder blades, then let go. In a well-hydrated dog, the skin usually springs back into place almost straight away. In a dehydrated dog, it may fall back slowly or stay up in a ridge (a "tent").
This is only a rough guide. Older dogs, thin dogs and some breeds with loose skin naturally have less springy skin, and overweight dogs can look fine even when they're dehydrated. It's most useful if you try it when your dog is well, so you know what normal looks like for them.
The capillary refill test
Lift your dog's lip and press a fingertip on a pink part of the gum until it goes pale. Let go and count. The pink colour should return in about 2 seconds. If it takes longer, blood flow may be reduced, which can happen with dehydration, shock or other serious problems.
If your dog's gums are naturally dark, this test is harder to read. Gums that are very pale, white, grey, blue or bright red are a reason to call a vet straight away.
What causes dehydration in dogs?
- Heat and exercise. Dogs cool down mainly by panting, which uses up water. Hot days, warm cars and hard exercise all raise water loss.
- Vomiting and diarrhoea. These can drain water and salts quickly, especially in puppies, small dogs and older dogs.
- Illness. Kidney disease, diabetes and some hormone problems can make a dog pee much more and lose water. A fever also raises water needs.
- Not enough water access. A bowl that's been knocked over, a frozen water dish in winter, a long car journey or a day out without water can all leave a dog short.
- Not wanting to drink. Nausea, pain, dental problems or simply feeling unwell can stop a dog drinking enough.
How much water does a dog need?
A commonly quoted guide is about 50 to 60 ml of water per kg of body weight per day. By that guide, a 10 kg dog would drink roughly 500 to 600 ml a day. That's a starting point, not a target. Dogs on wet food get some water from their meals and may drink less. Dogs who are active, nursing puppies or out in the heat need more.
What matters most is change. A dog who suddenly drinks a lot more, or a lot less, than usual for several days should see a vet.
What to do if you think your dog is dehydrated
- Offer small amounts of fresh water often. A few laps every few minutes is better than letting a thirsty dog gulp a whole bowl, which can make some dogs vomit.
- Move them somewhere cool and shaded. Indoors with a fan, or in the shade outside. Rest is better than activity.
- Watch closely. If they drink, keep it down and perk up, that's a good sign. Keep checking their gums and energy.
- Call your vet if signs don't improve quickly, if you're not sure, or if your dog is a puppy, a senior or has a health condition.
Is vomiting or has diarrhoea and can't keep water down, is very weak or collapses, has very pale, grey or bright red gums, has sunken eyes and very sticky gums, or may have heatstroke. Severe dehydration often needs fluids given by a vet, under the skin or into a vein.
Heatstroke: a related emergency
Heatstroke is when a dog's body overheats. Dehydration and heatstroke often happen together. Signs include heavy panting, drooling, a bright red tongue or gums, confusion, wobbling, vomiting and collapse. Flat-faced breeds, overweight dogs and older dogs are at higher risk.
If you suspect heatstroke, move your dog somewhere cool and start cooling them with cool (not ice-cold) water and air flow, then get to a vet as quickly as you can. Phone ahead while you travel. Never leave a dog in a parked car on a warm day, even with the windows open.
Don't reach for human drinks
Sports drinks and other electrolyte drinks made for people are not designed for dogs. Many contain sugar, artificial sweeteners or salt levels that may not be right for a dog, especially one who is already unwell. Don't give them without your vet's advice. If your dog needs extra salts, your vet can recommend a product made for pets and the right amount.
FAQ
How can I tell if my dog is dehydrated at home?
Check the gums (they should be moist and slippery), look at the eyes, gently lift the skin over the shoulders and see how quickly it settles, and press a gum to check the colour comes back in about 2 seconds. These are rough guides, not a diagnosis.
How much water should a dog drink a day?
A commonly quoted guide is about 50 to 60 ml per kg of body weight per day. It varies with heat, exercise, diet and health, so watch for big changes rather than exact amounts.
Can I give my dog sports drinks or electrolyte drinks?
Not without vet advice. Drinks made for people often contain sugar, sweeteners or salt levels that aren't right for dogs. Your vet can recommend a pet rehydration solution if it's needed.
Should I force my dog to drink?
No. Offer small amounts often. Don't squirt water into the mouth of a weak or collapsed dog, as they could breathe it in. Get them to a vet instead.
Is dehydration an emergency?
Mild dehydration can often be fixed by drinking. Severe dehydration, or dehydration with vomiting, diarrhoea, collapse or heatstroke, is an emergency.
Home checks are a rough guide only. If you're worried, call your vet.
