Dog drinking more water than usual (polydipsia)
A persistent increase in thirst is rarely benign in dogs — book a vet appointment within a few days; sooner if accompanied by vomiting, weight loss, or unspayed female dogs after a season.
Recognise the signs
- Empty water bowl more often than usual
- Drinking from puddles, baths, toilets
- Urinating much more, larger puddles, accidents in the house
- Often drinking is noticed before urination changes
- Other signs: weight loss, increased appetite, lethargy, vomiting, vaginal discharge in unspayed females
First aid steps
- Measure water intake for 24–48 hours: refill the bowl with a measured amount, top up with measured water, total at the end of the day.
- Normal is roughly 50ml per kg of dog per day; over 100ml/kg/day is clearly excessive.
- Note any other changes — appetite, weight, urination, vaginal discharge.
- Phone the vet for a routine appointment within a few days, or sooner if any concerning signs.
Do NOT
- Do not restrict water — most causes worsen with dehydration.
- Do not assume hot weather alone explains persistent increased thirst.
- Do not delay if the dog is an unspayed female within 8 weeks of a season — pyometra is an emergency.
- Do not start salt-restricted diets without vet input.
When to phone the vet immediately
- Unspayed female dog with increased thirst within 8 weeks of a season
- Vomiting, lethargy, off food alongside increased thirst
- Sudden severe thirst with weakness or collapse
- Suspected toxin ingestion (antifreeze, rodenticide)
Signs that can usually wait for a routine appointment
- Mild transient increased thirst on a hot day or after exercise, in an otherwise bright dog, can be monitored briefly.
Common causes
- Diabetes mellitus
- Kidney disease
- Cushing's disease (hyperadrenocorticism)
- Pyometra in unspayed females
- Liver disease
- Diabetes insipidus (rare)
- Steroid medication
- High-salt food or treats
- Hot weather, exercise, lactation (normal)
What the vet will need to know
- Estimated daily water intake
- Recent appetite, weight, energy changes
- Urination changes
- Spay status and date of last season for entire females
- Current medications, especially steroids
- Recent diet changes
Aftercare
- Investigation typically includes urinalysis, bloods, and sometimes ultrasound.
- Treatment depends on cause — insulin for diabetes, kidney support, pyometra surgery, Cushing's medication.
- Most causes need lifelong management.
- Repeat tests at intervals to monitor.
Prevention
- Annual checks with bloods from middle age onwards.
- Spay female dogs not intended for breeding.
- Avoid high-salt treats and human food.
- Maintain healthy weight.
Breed-specific notes
- Diabetes higher in: Samoyed, Tibetan Terrier, Cairn Terrier, Miniature Schnauzer.
- Cushing's higher in: Poodles, Dachshunds, Yorkshire Terriers, Boston Terriers.
- Pyometra: see dog-pyometra entry.
Frequently asked questions
How much should a dog drink per day?
Roughly 50ml per kg of body weight per day, varying with weather, activity, and diet (wet food provides much of the water). Over 100ml/kg consistently is significantly excessive and warrants vet investigation.
Is increased thirst always serious?
Brief increases due to weather, exercise, or salty food are usually harmless. Persistent increased thirst lasting more than a few days, or any thirst increase with other symptoms, almost always reflects an underlying problem worth investigating.
Can I just measure water for a few days first?
Yes — a 24-48 hour measurement is genuinely helpful for the vet. Just don't delay the appointment beyond a week if the increase is real, and don't measure if the dog seems unwell — go straight to the vet.