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Noticing your older dog draining the water bowl faster than usual can feel unsettling, especially if it seems to come out of nowhere. Sometimes it really is something simple, like warmer weather or a switch to salty treats. But in senior dogs, increased thirst is also a classic early clue for several medical problems that are easier to manage when caught early.
This article will walk you through what “too much” can look like, the most common medical reasons behind it, what you can safely do at home, and what your veterinarian is likely to check.
Important: Do not restrict your dog’s water at home unless your veterinarian gives you a specific plan. Increased drinking is often your dog’s attempt to stay safe and hydrated. And as always, please check with your dog’s veterinarian, especially if this change is new, dramatic, or paired with other symptoms.
First, what counts as “drinking too much”?
Dogs do not all drink the same amount. Water needs change with heat, exercise, stress, diet (dry food vs canned), and even household routines.
That said, veterinarians use rough thresholds when deciding whether increased drinking is medically meaningful. A commonly cited guideline is that water consumption over about 100 mL per kilogram of body weight per day is considered abnormal and worth investigating. This same source also cautions that these numbers were established in laboratory dogs and may not perfectly represent real-life pets, so they are best used as a guide rather than a strict rule.
A practical way to measure water at home (without obsessing)
If your dog has a single main water source, you can:
- Measure how much water you put in the bowl (in mL or ounces).
- After 24 hours, measure what is left and subtract.
- Add any refills you gave during the day.
- Try to do this for 2 to 3 days for a clearer average.
This can be very helpful information for your vet. VCA specifically notes that measuring 24-hour intake helps determine severity and guide the workup.
If multiple pets share bowls, your dog drinks outdoors, or you use an auto-fountain, measurement is harder. In that case, your observations still matter: more frequent refills, waking at night to drink, or suddenly empty bowls are all useful details to report.
When increased drinking is more urgent
Call your vet promptly (same day or within 24 hours) if increased drinking comes with any of the following:
- Vomiting, diarrhea, refusal to eat, unusual tiredness
- Noticeable weight loss despite normal appetite
- Accidents in the house or dramatically increased urination
- Weakness, collapse, confusion, or severe lethargy
- A sweet or “fruity” breath odor, rapid breathing, or sudden decline (possible diabetic crisis)
- Unspayed female dog with lethargy, discharge, swollen belly, or being “off” after a heat cycle (possible pyometra)
Pyometra (uterine infection) can be life-threatening and is specifically associated with increased thirst and urination among other signs.
The most common medical reasons in senior dogs
Vets often talk about “PU/PD,” meaning polyuria/polydipsia: increased urination and increased thirst. In many dogs, the increased drinking is happening because the body is losing more water in urine, so the dog drinks to keep up.
A stepwise review in Today’s Veterinary Practice notes that the most common causes of PU/PD in dogs include chronic kidney disease, diabetes mellitus, and hyperadrenocorticism (Cushing’s disease).
Below are the big categories your veterinarian will consider.
Chronic kidney disease or other kidney dysfunction
Kidneys help regulate water balance and concentrate urine. When kidney function declines, urine often becomes more dilute and the body loses more water, triggering thirst.
Merck’s veterinary reference describes chronic kidney disease (CKD) as typically developing over months or years, often becoming noticeable only after significant changes have already occurred. That “quiet progression” is part of why increased thirst in a senior dog should be taken seriously even if they still seem mostly normal.
What you might also notice:
- More frequent urination or larger urine clumps/puddles
- Appetite changes, nausea, weight loss, bad breath, lower energy (more common later)
Diabetes mellitus
Diabetes mellitus is a common endocrine disease in dogs, and the classic signs include increased urination and thirst, often paired with increased appetite and weight loss. Merck describes these clinical signs as reflecting high blood sugar with glucose spilling into the urine (which pulls extra water along with it).
What you might also notice:
- Ravenous appetite with weight loss
- Peeing much more than usual, sometimes accidents
- Recurrent infections (skin, ears, urinary tract)
- In advanced cases, vomiting, weakness, dehydration, rapid breathing (urgent)
If diabetes is suspected, diagnosis is not guesswork. It is confirmed with blood and urine testing.
Cushing’s disease (hyperadrenocorticism) or steroid exposure
Cushing’s disease is caused by chronic excess cortisol, usually in middle-aged to older dogs. Merck notes it occurs predominantly in dogs around 7 to 12 years old, and describes how most cases are pituitary-dependent.
Many dogs with Cushing’s show:
- Increased thirst and urination
- Increased appetite
- Panting, pot-bellied appearance, muscle loss
- Skin changes (thinning, hair loss, recurrent infections)
Also important: excessive thirst can happen from steroid medications (like prednisone) or certain topical steroid exposures. VCA lists corticosteroids, anticonvulsants, and diuretics among drugs that can increase thirst and urination, which is why your vet will want a full medication and supplement list.
Urinary tract infection or kidney infection
A urinary tract infection can cause frequent urination and sometimes increased drinking. In seniors, UTIs can also show up as:
- Accidents in the house
- Straining, frequent squatting, licking
- Blood in urine (not always)
Your vet will usually check urine for signs of infection and may recommend a culture depending on the situation.
Liver disease and other metabolic issues
Some liver conditions can be associated with changes on a blood chemistry panel and may show up in the workup of increased thirst and urination. VCA notes that elevated liver enzymes on blood testing could point toward liver disease or Cushing’s, among other possibilities.
Other metabolic causes your vet may consider (depending on exam and labs) can include electrolyte abnormalities like high calcium, some cancers, and rarer hormone disorders.
Diabetes insipidus and other uncommon causes
Diabetes insipidus is much rarer than diabetes mellitus. It involves problems with antidiuretic hormone signaling, leading to very dilute urine and pronounced thirst. This is not something you can diagnose at home, and testing must be done carefully.
Specialized tests exist, but even veterinary references emphasize caution. A Today’s Veterinary Practice PDF notes that a modified water deprivation test is rarely indicated and should not be performed in certain higher-risk patients (for example, those with dehydration or kidney-related abnormalities).
That is one reason why it is so important not to experiment with water restriction on your own.
What you can do at home right now
Here are safe, useful steps that genuinely help your veterinarian without putting your dog at risk.
Keep water freely available
Do not limit water unless your veterinarian specifically instructs you to. If your dog is losing more water through urine, restricting intake can worsen dehydration and make them sicker.
Start a simple symptom log
Write down:
- When you first noticed the change
- Any increase in urination, accidents, or nighttime wake-ups
- Appetite changes, weight change (even a rough estimate), vomiting/diarrhea
- New meds, treats, supplements, or diet changes
- Heat exposure and activity changes
Measure water intake if you can
Even 1 to 3 days of rough numbers can help your vet triage urgency and choose the best first tests.
Check for the “hidden” normal explanations
These do not rule out disease, but they can contribute:
- Switching from canned to dry food
- More salty treats (jerky-style treats, cheese, deli meats)
- Hotter weather, more exercise
- Stress changes (new home, visitors, schedule changes)
If the behavior persists beyond a day or two, or it is dramatic, it still deserves medical attention even if you found a possible trigger.
What your veterinarian will likely do
Most vets approach PU/PD in a structured way: history, physical exam, then targeted lab tests. VCA describes the workup beginning with a complete history and exam, followed by tests such as blood chemistry and urinalysis to evaluate organ function and metabolic state.
Common first-line tests include:
- Urinalysis (checks concentration, glucose, infection markers, crystals)
- Blood chemistry panel (kidney values, liver enzymes, electrolytes, glucose)
- Complete blood count
- Often additional tests based on results (urine culture, imaging, endocrine testing)
For senior dogs, routine wellness testing is commonly recommended because older pets have a higher risk of underlying disease. VCA outlines senior wellness testing categories including CBC, biochemistry profile, urinalysis, and thyroid testing. The AAHA Senior Care Guidelines also emphasize a tailored senior healthcare plan that includes preventive and diagnostic protocols.
Treatment depends on the cause, not the symptom
It is tempting to look for ways to “stop the drinking.” But thirst is often protective.
Examples:
- Diabetes mellitus is managed with insulin and diet changes under veterinary guidance.
- CKD management may include diet therapy, hydration strategies, and treating contributing issues depending on stage.
- Cushing’s disease may require endocrine testing and medical or surgical management depending on type.
- UTIs require appropriate antibiotics and sometimes culture-based selection.
The right plan is built from exam findings and lab results, not from guessing based on one symptom.
Where research is limited (and why that matters)
Even when veterinary medicine has strong clinical experience, some “numbers” owners see online can be less precise than they look.
One example is the commonly quoted water-intake threshold for polydipsia. The VIN proceedings note the 100 mL/kg/day cutoff and explicitly caution that these values come from laboratory-reared dogs and may not reflect normal variation in household pets.
That does not mean the guideline is useless. It means it should be interpreted alongside your dog’s real-world context, your veterinarian’s exam, and objective testing.
Bottom line
A senior dog suddenly drinking much more water is not something to ignore. The most common explanations include kidney disease, diabetes mellitus, and Cushing’s disease, but infections, medications, and other metabolic problems are also on the list.
The safest, most helpful steps are:
- Keep water available
- Measure intake if possible
- Log symptoms and changes
- Book a veterinary visit for evaluation
And again, please check with your dog’s veterinarian about your specific dog and situation.
Sources
- VCA Animal Hospitals: “Testing for Increased Thirst and Urination” (Vca)
- Today’s Veterinary Practice: “A Stepwise Diagnostic Approach to Polyuria and Polydipsia” (Today's Veterinary Practice)
- Merck Veterinary Manual: “Diabetes Mellitus in Dogs and Cats” (Merck Veterinary Manual)
- Merck Veterinary Manual: “Renal Dysfunction in Dogs and Cats” (Merck Veterinary Manual)
- Merck Veterinary Manual: “Cushing Disease (Pituitary-Dependent Hyperadrenocorticism)” (Merck Veterinary Manual)
- AAHA: 2023 Senior Care Guidelines for Dogs and Cats and related resource page (AAHA)
- AAHA: 2018 Diabetes Management Guidelines (2022 update PDF) (AAHA)
- VIN WSAVA Proceedings: PU/PD water intake guideline and limitations (vin.com)