Why Is My Dog Drinking So Much Water?
If you've noticed your dog emptying the water bowl more quickly than usual, or asking to go outside to urinate more frequently, it's worth taking notice. Excessive thirst — known medically as polydipsia — can be a symptom of several serious conditions. The good news is that most causes are treatable if caught early.
Key takeaways
- Excessive thirst (polydipsia) in dogs is often a sign of a medical condition — the most common causes include diabetes, kidney disease, and Cushing's syndrome.
- Never restrict your dog's water intake without vet guidance, as dehydration can rapidly worsen most underlying causes.
- A blood test and urinalysis are the key first-line diagnostics, typically costing £80–£150 at a UK vet.
How Much Water Should a Dog Drink?
As a general rule, dogs should drink approximately 50–60ml of water per kilogram of body weight per day. A 20kg dog, for example, should drink around 1–1.2 litres daily. This varies with activity level, diet (dry food requires more water intake than wet food), ambient temperature, and health status.
To assess whether your dog is drinking excessively, it can be helpful to measure water intake for 24 hours — fill the bowl with a measured amount, note how much remains after 24 hours, and account for any water your dog drinks elsewhere. This gives your vet useful baseline data.
Increased thirst becomes clinically significant (polydipsia) when intake exceeds roughly 100ml/kg/day. However, even more modest increases that are clearly a change from your dog's normal baseline are worth discussing with your vet. Increased urination (polyuria) almost always accompanies polydipsia — if your dog is asking to go out more frequently or having accidents indoors, this supports the need for a veterinary assessment.
Common Medical Causes of Excessive Thirst
The most frequently diagnosed causes of polydipsia/polyuria in dogs include: diabetes mellitus, where inadequate insulin causes glucose to accumulate in the blood and spill into the urine, drawing water with it; Cushing's syndrome (hyperadrenocorticism), a common hormonal condition in middle-aged and older dogs where excess cortisol is produced; chronic kidney disease, which is very common in older dogs and impairs the kidney's ability to concentrate urine; and pyometra, a uterine infection that occurs in entire female dogs and is a medical emergency.
Other causes include: Addison's disease (the opposite of Cushing's — too little cortisol); hypercalcaemia (high blood calcium, sometimes associated with cancer); liver disease; and certain medications — notably corticosteroids and diuretics — which increase thirst as a side effect.
Excessive thirst can also have behavioural or psychological causes in some dogs, but these are less common and should only be considered once medical causes have been ruled out by blood and urine tests.
What Happens at the Vet
Your vet will take a detailed history, asking about the onset and degree of increased drinking, any changes in urination, appetite, or weight, and any relevant medical history or medications. A physical examination will be performed.
The most important diagnostic tests are a blood biochemistry panel — checking kidney function, liver enzymes, blood glucose, calcium, and other markers — and a urine analysis (urinalysis). Together, these tests can identify most of the common causes of polydipsia. They typically cost £80–£150 at a standard practice.
Depending on the results, further tests may be needed — for example, an ACTH stimulation test for Cushing's, abdominal ultrasound for pyometra or adrenal abnormalities, or urine protein-to-creatinine ratio for kidney disease. Your vet will guide you through the appropriate diagnostic pathway.
Do Not Restrict Your Dog's Water Intake
It can be tempting to restrict water intake if your dog is drinking excessively — particularly if it is leading to accidents indoors. However, restricting water access is dangerous and should never be done without specific veterinary advice. Most causes of polydipsia involve the kidneys producing large volumes of dilute urine, and restricting water can quickly lead to dehydration and make the underlying condition worse.
If indoor accidents are a problem while you wait for a diagnosis, consider more frequent outdoor trips and, if necessary, puppy pads indoors. Once the underlying cause is identified and treated, drinking and urination should return towards normal.
If your dog is also showing signs of vomiting, lethargy, reduced appetite, or has an obviously enlarged abdomen (which may indicate pyometra or Cushing's), seek veterinary attention urgently — do not wait for a routine appointment.
Finding Affordable Diagnostics Near You
Investigating excessive thirst typically requires blood tests and urinalysis, and the cost can vary between practices. A blood biochemistry panel plus urinalysis typically costs £80–£150 at a standard UK practice, but prices differ — sometimes significantly — between individual vets.
CompareMyVet at app.comparemyvet.uk helps UK pet owners find and compare local vet practices that publish their prices upfront. Understanding what diagnostic tests should cost in your area helps you budget and make informed decisions about where your pet receives care.
If ongoing medication is prescribed following a diagnosis — for conditions like diabetes, Cushing's, or kidney disease — ask your vet for a written prescription so you can source medication at a lower cost from a registered online pharmacy, as is your right under the March 2026 CMA reforms.
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Common questions
Yes, dogs drink more in hot weather, after exercise, or on a dry food diet — these are normal variations. However, if increased thirst persists in normal conditions, is significantly above usual levels, or is accompanied by other symptoms, a vet check is warranted to rule out underlying disease.
In most cases, no — but it depends on the accompanying signs. If your dog is also vomiting, lethargic, has a swollen abdomen, or is an entire female dog showing any of these symptoms (possible pyometra), seek emergency care. Otherwise, a same-day or next-day routine appointment is appropriate.
Cushing's syndrome (hyperadrenocorticism) typically presents in middle-aged to older dogs with increased thirst and urination, increased appetite, a pot-bellied appearance, hair loss (especially on the flanks), thin skin, and increased panting. It is diagnosed with specific blood tests and is managed with medication.
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