Increased thirst in dogs: Why is my dog drinking a lot of water?

dog drinking a lot of water
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If you’ve noticed your dog is drinking lots of water, it’s natural to be concerned. Changes in behaviour like excessive thirst can be a sign of illness or injury, but it’s important not to panic. There are a number of reasons that your dog could have developed an epic thirst.

It’s normal for dogs to drink a lot of water, especially on hot days or if they’ve been exercising vigorously. So, if your pooch downs a bowl of water after running around the yard for half an hour, that’s completely normal.

Dog’s can get some of the moisture they need from the best wet dog foods, so if you’re feeding them primarily with a dry food diet then they will probably increase their direct water intake to compensate. If you’ve just switched your pooch to one of the best dry dog foods, this would explain their increased thirst.

If there is no obvious cause, like hot weather or a dietary change, and if your dog’s increased thirst lasts for more than a few days, then we’d recommend taking your dog to see a vet so they can properly diagnose if there are any underlying issues. 

We spoke to expert vet Dr. Hannah Godfrey about the most common medical reasons for excessive thirst in dogs, and she offers advice on what to do if you notice a sudden change in your dog’s water intake.

Dr. Hannah Godfrey BVetMed MRCVS
Dr Hannah Godfrey

Dr Hannah Godfrey studied Veterinary Medicine at the Royal Veterinary College London. After graduating in 2011, Dr Godfrey went on to become a veterinary surgeon, conducting surgery consultations on a range of animals at a small independent practice in Cardiff, South Wales, UK. Dr Godfrey has a strong interest in soft tissue surgery. When she’s not helping animals back on their feet, Dr Godfrey writes a number of veterinary and animal-focussed articles.

How much water should a dog drink a day?

Every dog is different, and the amount of water they drink will also depend on the temperature where they live and whether they're fed wet or dry food. However, the answer to how much water should my dog drink in a day is an upper threshold of 100 milliliters per kilogram of bodyweight. 

So, if your dog weighs 10kg, they shouldn’t drink more than 1000ml (1L) of water in a 24-hour period. If your dog drinks more than this in a day, it could be an indication of a medical condition.

dog drinking water

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Should I be concerned if my dog is drinking a lot of water?

If your dog is drinking more water than usual, there's no need to be immediately alarmed. There are lots of reasons why they might be extra thirsty. For instance, if they've done a lot of exercise or the weather has been hot, this could be the reason. 

It's also important to remember that any change in their diet could affect their thirst since different dog foods will contain different amounts of water. However, if you measure your dog's water intake on three separate days and find it averages at more than 100ml per kg bodyweight, it's time for a trip to the vet.

Why is my dog drinking a lot of water?

There are a lot of potential reasons for your dog is drinking a lot of water. We've broken down the top nine most common reasons below:

1. Hot weather or exercise

If it's especially hot outside or your dog has recently exercised, you're more likely to notice them lapping up an increased amount of water.

2. Fever or infection

If your furry friend is fighting an infection and has a high temperature, they might drink more to try to cool off.

Sick dog lying on the couch

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3. Vomiting

Vomiting causes fluid loss, which can make your dog dehydrated. They might drink more to try to rehydrate. However, filling their stomach with water might cause them to vomit even more, so fluid should be offered regularly in small amounts.

4. Diarrhea

Like vomiting, diarrhea also causes fluid loss and can lead to dehydration. You might notice your dog drinking more if they have diarrhea, but they should return to normal once the diarrhea has resolved.

Image of dog feeling poorly

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5. Diabetes mellitus

Diabetes mellitus can cause your dog to be more thirsty and to pee more often. You might also notice them losing weight despite being hungry, and they might develop cataracts in their eyes. If diabetes isn't treated, it can lead to ketoacidosis, which causes vomiting, dehydration, and shock. 

See our full guide on Diabetes mellitus in dogs for more information.

6. Pyometra

If your female dog isn't neutered, they are at risk of a condition called pyometra. This is when bacteria enter the womb and cause infection. If the cervix is open, the infection can drain out, and you might see a vaginal discharge.

If the cervix is closed, the pus is trapped within the womb, causing the dog to deteriorate quickly. Both types of pyometra can sadly be fatal if not treated promptly. If your dog has a pyometra, they might also vomit, stop eating or become more lethargic.

7. Cushing’s disease

Cushing's disease is also known as hyperadrenocorticism. It occurs when the adrenal gland produces too much of the stress hormone cortisol. If your dog has Cushing's disease, they will be really thirsty and pee lots. 

They might also look pot-bellied, with thin skin or hair loss. Dogs with Cushing's disease often pant a lot, even when they're not exerting themselves. If left untreated, Cushing's can lead to diabetes and problems with the heart and lungs.

See our full guide on Cushing’s disease in dogs for more advice.

dog lying on sofa

(Image credit: Getty Images)

8. Kidney disease

Your dog's kidneys are responsible for controlling urine output and maintaining hydration. If they aren't working as well as they should, this can cause an increase in thirst and urination. On top of these symptoms, dogs with kidney disease often lose weight, vomit, and go off their food.

9. Liver disease

Some types of liver disease can cause your dog to drink more. You might also notice them eating less, suffering from vomiting or diarrhea, and acting quiet and lethargic. Some kinds of liver disease can cause jaundice, where the skin, eyes, and gums begin to look yellow-orange.

When to visit the vet

If you think your dog is drinking too much water, it's worth measuring the amount they drink first. Do this by adding a known amount of water to their bowl — say, a litre — and subtracting any water left in their bowl 24 hours later. If you need to top the bowl up, don’t forget to make a note of how much extra you add. 

If your dog drinks more than 100ml per kilogram in a 24-hour period, then it's time to take them to a vet. However, water intake amounts less than this can be abnormal too, so trust your instincts. It's best if you can keep a diary or a mental note of any other symptoms they might have. If your dog is suddenly drinking a lot and seems unwell or is vomiting, you should seek veterinary advice immediately rather than waiting to take measurements.

Many things can cause your pooch to drink more than they normally would. Thankfully, there's a simple calculation that can let you know whether their thirst is excessive or not. However, if you think your dog is drinking a lot of water and you’re worried, it's best to book a check-up with their vet, even if the calculation says that they may be normal. 

Is your pup off their food? An expert vet walks you through the things to check when your dog is not eating and shares some simple ways that you can stimulate their appetite.

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Dr. Hannah Godfrey BVetMed MRCVS

Dr Hannah Godfrey is a small animal vet who graduated from the Royal Veterinary College in 2011 and began work straight away at a busy mixed practice. Initially, she treated all species, but focussed on small animals from 2014. She has a passion for soft tissue surgery, ultrasound, and canine and feline dentistry, having completed additional training in these areas.