Noticing that your senior pet is suddenly draining their water bowl faster than usual, or asking to go outside more often to urinate, is one of those changes that is easy to dismiss at first. Pets age, habits shift, and it can feel like a minor thing. But increased thirst, known clinically as polydipsia, is actually one of the more reliable early warning signs of several common conditions in older cats and dogs, and it is rarely something to simply monitor and forget about.
This guide explains what counts as increased thirst, the most common underlying causes in senior pets, and what steps to take if you notice it in your own cat or dog.
Quick Summary: A noticeable, sustained increase in water intake in a senior pet is usually a sign of an underlying medical condition rather than simple ageing, with kidney disease, diabetes, and hyperthyroidism (in cats) among the most common causes. Track your pet's water intake if possible, note any accompanying symptoms such as weight change or increased urination, and see a vet promptly rather than waiting, since many of these conditions are far easier to manage when caught early.
What Counts as "Increased" Thirst?
It can be hard to judge water intake accurately when you are not measuring it directly, especially in multi-pet households or homes with multiple water sources. As a general guide, cats typically drink somewhere in the region of 50 to 60 millilitres per kilogram of body weight per day (though a large proportion of this normally comes from wet food rather than the water bowl), and dogs typically drink somewhere in the region of 50 to 100 millilitres per kilogram per day, though this varies with diet, activity, and climate. If you notice your pet's bowl needing refilling far more often than it used to, if they are visiting the water bowl more frequently throughout the day, or if you notice more frequent urination, larger volumes of urine, or accidents in a previously reliable pet, these are all signs worth paying attention to.
Why Increased Thirst Becomes More Common With Age
Several of the conditions that cause increased thirst become substantially more common as pets age, which is why this symptom deserves particular attention in senior cats and dogs even when it develops gradually. The kidneys, thyroid, and pancreas are all organs whose function can decline with age, and dysfunction in any of them can drive increased water intake as the body attempts to compensate.
Kidney Disease
Chronic kidney disease is extremely common in older cats, and also affects a significant number of senior dogs. As kidney function declines, the kidneys become less able to concentrate urine, so the body loses more water than it should, and the pet compensates by drinking more. Alongside increased thirst, watch for increased urination, weight loss, reduced appetite, and lethargy. Kidney disease is a progressive condition, but with early diagnosis, prescription kidney-support diets and other management strategies can meaningfully slow its progression and support quality of life for a considerable time.
Diabetes Mellitus
Diabetes affects both cats and dogs, and increased thirst alongside increased urination is one of the classic early signs. In diabetes, the body either does not produce enough insulin or does not use it effectively, leading to elevated blood sugar. As excess sugar is excreted in the urine, it draws additional water with it, driving the excessive thirst and urination. Other signs include increased appetite despite weight loss, and in cats, a distinctive flat-footed walking stance can sometimes develop in advanced, poorly managed cases. Diabetes is manageable in both species with appropriate veterinary treatment, typically involving insulin therapy and dietary management.
Hyperthyroidism in Cats
An overactive thyroid gland is one of the most common hormonal conditions in senior cats, and increased thirst is a frequent accompanying symptom, alongside increased appetite, weight loss despite eating more, restlessness, and a faster heart rate. Hyperthyroidism is generally very treatable, with options including medication, a specialised prescription diet, or more permanent treatments such as radioactive iodine therapy or surgery, depending on the individual cat and vet recommendation.
Cushing's Disease in Dogs
Cushing's disease, caused by excess cortisol production, is a condition seen particularly in middle-aged and senior dogs. Increased thirst and urination are hallmark signs, often alongside a pot-bellied appearance, hair loss, thinning skin, and increased panting. Diagnosis usually requires specific hormonal testing, and treatment options depend on the underlying cause, which can include a pituitary or adrenal gland issue.
Liver Disease
Various forms of liver dysfunction can also drive increased thirst in senior pets, often alongside other signs such as jaundice (a yellowish tinge to the gums or eyes), vomiting, or changes in appetite. Liver conditions vary widely in cause and severity, so veterinary investigation is important to identify the specific issue and appropriate treatment path.
Medication Side Effects
Certain medications commonly prescribed to senior pets, including some steroids and diuretics, can increase thirst as a known side effect. If your pet has recently started a new medication and you notice increased water intake, mention this to your vet, since it may simply be an expected effect of the treatment rather than a sign of a new problem, though it is always worth confirming rather than assuming.
Tracking Your Pet's Water Intake
If you suspect your pet is drinking more than usual but are not certain, tracking their intake for a few days can provide useful, objective information for your vet. Measure the water you put into their bowl or fountain at the start of the day and measure what remains at the end (accounting for any spillage or evaporation as best you can), noting the total consumed. This is easier with a fountain that has a clear or marked reservoir, such as the ROJECO 3.2L Stainless Steel Cat Water Fountain, which lets you see the water level at a glance rather than needing to empty and remeasure a bowl each time.
What to Do If You Notice Increased Thirst
Book a veterinary appointment rather than waiting to see if it resolves on its own. Bring notes on how long you have noticed the change, roughly how much more your pet seems to be drinking, and any other changes you have observed, such as appetite, weight, energy levels, or litter box and toileting habits. Your vet will likely recommend blood and urine tests, since these are the primary tools for identifying which of the conditions above, if any, is responsible. Many of these conditions share overlapping symptoms, so testing is really the only reliable way to distinguish between them.
Should You Ever Restrict Water?
No. Regardless of the underlying cause, never restrict a pet's access to water in response to increased thirst. Increased drinking is almost always the body's response to an underlying issue causing excessive fluid loss, and restricting water intake in this situation can be dangerous, potentially leading to dehydration on top of whatever the original problem is. Always allow free access to fresh water while you investigate the cause with your vet.
Supporting Hydration in Senior Pets Generally
Whether or not increased thirst turns out to reflect an underlying condition, supporting good hydration is valuable for all senior pets, since many are also prone to reduced kidney function and general fluid needs as they age. Having multiple water sources around the home, particularly for pets with mobility issues who may not want to travel far, and considering a flowing water fountain, which many cats and dogs find more appealing than a static bowl and which can encourage naturally low drinkers to take in more fluid, are both worthwhile. A fountain such as the ROJECO 2.5L Cat Water Fountain provides continuously circulating, filtered water that many pets find more enticing than a still bowl.
Final Thoughts
Increased thirst in a senior pet is a symptom worth taking seriously rather than dismissing as simply part of getting older. While it can occasionally have benign explanations, such as warmer weather or a recent diet change, it is frequently an early indicator of a treatable medical condition. Prompt veterinary investigation gives you and your pet the best chance of catching and managing whatever is behind it, often with a considerably better long-term outcome than if the sign is left unaddressed.
Explore our range of fountains and hydration support products at Rojeco.
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