Why is my dog drinking more water than usual — and when should you worry?
At a glance
- A dog drinking more than 100ml per kg of body weight per day is showing a clinical sign — this is called polydipsia.
- Common causes include hot weather, increased exercise, a change in diet, or eating salty food.
- More serious causes include diabetes, kidney disease, Cushing's disease, pyometra, and liver disease.
- Polydipsia almost always comes with increased urination (polyuria) — the two symptoms go together.
- If excessive drinking lasts more than 48 hours or appears alongside other symptoms, see a vet promptly.
How much water should a dog drink in a day?
A healthy dog drinks between 50ml and 100ml of water per kg of body weight per day. So a 10kg Cocker Spaniel drinks roughly half a litre. A 30kg Labrador can drink up to 3 litres. Anything above 100ml per kg, consistently, is considered excessive and has a clinical name: polydipsia.
That threshold matters because it gives you a concrete benchmark. You do not need to obsessively measure every bowl — but if your dog is draining the water bowl multiple times a day and you have not changed anything obvious, that is worth paying attention to.
Increased thirst in dogs almost always comes with increased urination. The two symptoms are so closely linked that vets refer to them together as PU/PD (polyuria and polydipsia). If your dog is drinking a lot more and urinating a lot more, that pairing is a meaningful clinical signal. It features in the wider picture of how diet and health conditions interact in dogs, and it is one of the first things a vet will ask you about.
What are the everyday reasons a dog might drink more?
Not every increase in thirst points to illness. Several ordinary things push water intake up temporarily.
- Hot weather or a warm house — dogs cool themselves through panting, which loses water fast.
- More exercise than usual — higher activity means higher fluid loss through panting and exertion.
- Salty food or treats — sodium increases thirst, just as it does in humans.
- A switch to dry food — kibble contains roughly 8–10% moisture. Fresh or wet food sits at 70–80% moisture. Dogs moving from fresh food to kibble typically drink significantly more to compensate.
- Certain medications — steroids (like prednisolone) are a well-known cause of increased thirst and urination in dogs.
If the change in drinking lines up with one of these factors and resolves within a day or two, it is usually nothing to worry about. The concern starts when there is no obvious explanation and the change persists.
What medical conditions cause excessive thirst in dogs?
When there is no simple lifestyle explanation, increased thirst points toward a medical cause. These are the most common ones a vet will investigate.
| Condition | What it does | Other signs to watch for |
|---|---|---|
| Diabetes mellitus | Excess glucose in the blood spills into urine, pulling water with it | Weight loss, increased appetite, cloudy eyes (cataracts) |
| Chronic kidney disease | Damaged kidneys cannot concentrate urine, so more water is needed | Weight loss, reduced appetite, bad breath, vomiting |
| Cushing's disease (hyperadrenocorticism) | Excess cortisol disrupts fluid regulation | Pot belly, hair loss, muscle weakness, panting |
| Pyometra | Infected uterus releases toxins that affect kidney function | Intact female, vaginal discharge, lethargy, off food |
| Liver disease | Impaired liver function disrupts normal fluid and toxin processing | Yellowing of skin or eyes, vomiting, weight loss |
| Hypercalcaemia | High blood calcium directly stimulates thirst | Lethargy, vomiting, constipation |
| Diabetes insipidus | Rare — the body cannot produce or respond to the hormone that regulates water retention | Enormous volumes of very dilute urine |
If your dog is showing any of the accompanying symptoms alongside increased thirst, do not wait. See a vet as soon as possible. Early diagnosis of conditions like diabetes or kidney disease significantly improves long-term outcomes.
When should you actually call the vet?
Call your vet if your dog has been drinking excessively for more than 48 hours with no clear cause. Call sooner if any of the following are also present:
- Lethargy or unusual weakness
- Vomiting or loss of appetite
- Weight loss over days or weeks
- Changes in urination frequency or colour
- Your dog is an intact female and seems unwell
- Your dog is on long-term medication
At the appointment, your vet will likely run blood and urine tests. A urine specific gravity test tells them whether the kidneys are concentrating urine normally. Blood panels check glucose, kidney markers, liver enzymes, and calcium levels. From those results, they can usually identify the cause or rule out the most serious options quickly.
Diet genuinely matters here too. Dogs eating high-moisture fresh food naturally drink less water at the bowl, because their meals are supplying a large proportion of their daily fluid intake. Marleybones Pantry Fresh meals contain around 70% moisture from real ingredients — no fillers, no added salt — which helps maintain steady hydration without spikes in thirst. If your dog recently switched to a drier food and their thirst shot up, that is the diet, not a disease.
Every dog is different — build your personalised Marleybones feeding and health plan tailored to your dog's age, size, and health requirements.
For dogs with confirmed kidney disease, diet becomes part of the treatment plan. Managing weight and food quality is relevant to kidney health because excess weight puts additional strain on the organs. Your vet will advise on specific nutritional targets — phosphorus levels in particular — for dogs with kidney issues.
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Frequently asked questions
Is it normal for a dog to drink more water in summer?
Yes. Dogs lose significant moisture through panting in hot weather, so thirst increases naturally. If your dog is drinking more during a heatwave or after exercise, that is normal thermoregulation. It should return to baseline once temperatures drop or rest is taken. Persistent thirst that continues regardless of temperature warrants a vet check.
Can a change in dog food cause increased thirst?
Yes, and this is one of the most common explanations. Dogs switching from wet or fresh food to dry kibble drink considerably more water because kibble contains only 8–10% moisture compared to 70–80% in fresh food. The body compensates by increasing thirst. Switching back to a higher-moisture diet typically resolves the issue without any medical intervention.
How do I measure how much my dog is drinking?
Fill a measuring jug to a known volume each morning and top up from the same jug throughout the day. Record total consumption at the end of the day. Do this for two or three consecutive days to get a reliable average. Subtract any water used for food preparation. Your vet will find this information useful at the consultation.
Could my dog be drinking more because they are stressed or anxious?
Stress can increase thirst in some dogs, particularly during significant life changes like a house move, a new baby, or rehoming. It is not the most common cause, but it is a real one. If stress is the suspected trigger, the thirst should reduce as the dog settles. If it does not settle within a week or two, book a vet appointment to rule out physical causes.
What does the vet do at a polydipsia appointment?
The vet takes a full history and asks about diet, medications, and any other symptoms. They then run blood tests and urinalysis. Key markers include blood glucose (for diabetes), urea and creatinine (for kidney function), cortisol or ACTH stimulation tests (for Cushing's), and urine specific gravity. Most causes can be identified or narrowed down in a single appointment. Some conditions, like diabetes insipidus, require additional water deprivation testing.
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