Dog Drinking More Water Than Usual: What It Can Mean

Increased thirst in dogs - polydipsia, if you want the clinical term - is one of those symptoms that's genuinely difficult to notice without a reference point. Most people don't know exactly how much water their dog drinks on a normal day. So when it increases, the change is often recognised retrospectively: you've been refilling the bowl more often, or you've noticed they're asking to go out more frequently, and it's only when it's been going on for a while that you think to mention it.

This matters because polydipsia is associated with several conditions that respond better to management when they're caught before the dog is showing more obvious signs of illness. It's worth knowing what to look for and how to establish a baseline before you need one. According to the PDSA PAW Mini Report 2025, there are now 11.1 million pet dogs in the UK - and with conditions like kidney disease, diabetes, and Cushing's syndrome more prevalent in older dogs, establishing water intake baselines while dogs are young and healthy is one of the most practical things owners can do.

What counts as excessive

The normal water intake for a healthy dog is roughly 50–100 ml per kilogram of body weight per day - so a 20 kg dog might drink between one and two litres. This varies with temperature, diet (wet food provides more moisture than dry), and activity level.

Polydipsia is typically defined as more than 100 ml per kilogram per day. But the specific number matters less than the change. A dog who suddenly starts emptying a water bowl that used to last all day, or who starts asking to go outside to urinate far more often than usual, is showing a change worth acting on.

How to measure if you're concerned

If you want a rough measurement: use a measuring jug to fill the bowl to a known amount in the morning. Record what's left at the end of the day, accounting for any food moisture if they eat wet food. Do this for three to five days. You'll have a usable number to give your vet.

It's not a perfect measurement - spillage, other household members topping it up, water from puddles on walks - but it's far more useful than "I think she's been drinking more."

Also note whether urination has increased alongside it. Polydipsia and polyuria (increased urination) usually come together, because most of the conditions that cause one also cause the other.

Conditions that commonly cause increased thirst

Diabetes mellitus is one of the most common causes. The body can't use glucose properly, so it accumulates in the blood and spills into the urine - taking water with it and driving thirst. Dogs with diabetes typically drink a lot, urinate a lot, and often lose weight despite a good or increased appetite. If you see increased thirst alongside unexplained weight loss, the combination warrants prompt veterinary assessment.

Cushing's syndrome (hyperadrenocorticism) causes the adrenal glands to overproduce cortisol. Increased thirst and urination are among the most consistent signs, often accompanied by a pot-bellied appearance, increased appetite, panting, and a thinning, poor-quality coat. It's most common in middle-aged to older dogs.

Kidney disease reduces the kidneys' ability to concentrate urine, so dogs urinate more dilute urine and drink more to compensate. Chronic kidney disease is common in older dogs and is often detected on routine blood and urine testing before dogs show obvious signs of illness.

Liver disease can drive polydipsia through several mechanisms. Associated signs include lethargy, reduced appetite, and occasionally jaundice (yellowing of the whites of the eyes or gums).

Pyometra - a serious uterine infection in unspayed females - commonly causes increased thirst as one of its symptoms, particularly in the open form where there's visible vaginal discharge. It's a surgical emergency. In an unspayed middle-aged or older female dog, increased thirst combined with any lethargy or changes in appetite warrants an urgent vet call.

Addison's disease (hypoadrenocorticism) causes increased thirst in some affected dogs, typically accompanied by lethargy, vomiting, and weight loss.

Certain medications - particularly corticosteroids (prednisolone and similar) - reliably cause increased thirst and urination as a direct side effect. If your dog has recently started steroids, this is expected and not a sign of a new problem. The PDSA PAW Mini Report 2025 noted that 64% of UK dogs are insured - which is particularly relevant for conditions like kidney disease and Cushing's syndrome, where long-term monitoring and management costs can be substantial.

When to call the vet

The conditions most commonly associated with increased thirst each have their own monitoring guides: diabetes, chronic kidney disease, and Cushing's syndrome.

Within a few days if:

• The increase has been going on for more than a week
• Urination has increased alongside it
• There are any other symptoms - lethargy, weight changes, increased appetite, vomiting

Same day if:

• Your dog is unspayed and also lethargic or off food (pyometra risk)
• There's any visible discharge from the vulva alongside the thirst
• The dog seems unwell in any way beyond just the drinking

Frequently Asked Questions

My dog drank a lot today but seems fine. Should I be worried? One day of drinking more - particularly in hot weather, after exercise, or if they ate something salty - isn't a concern. The pattern over several days is what matters. Note it and watch over the next week. If it continues or worsens, call your vet.

Can stress or anxiety cause increased thirst? Acute stress can temporarily increase thirst, but persistent polydipsia isn't typically explained by anxiety. If a stressful event (a house move, fireworks, a new pet) is followed by a brief increase in thirst that resolves within a day or two, it's likely situational. Ongoing increased thirst after the stressor has passed warrants investigation.

My older dog has started drinking more. Is that just old age? It's not a normal part of ageing and shouldn't be assumed to be. Older dogs are at higher risk for the conditions that cause polydipsia - kidney disease, Cushing's, diabetes - and these are worth identifying and managing early. A blood and urine test will often point to the cause.

How do I measure water intake accurately? Fill the bowl with a measured amount each morning, subtract what's left each evening. Do this for several days to get an average. It won't be perfectly accurate, but it gives you a concrete number rather than an impression - and a concrete number is what helps your vet assess significance.