Water and hydration

Water is the most essential nutrient of all, indispensable to every bodily function, which is why an animal can survive a prolonged energy deficit but a major loss of water becomes critical within a far shorter time. Needs vary with activity, ambient temperature, age, and crucially the [moisture](/glossary/moisture) content of the diet: an animal fed wet food drinks noticeably less because part of its requirement arrives through the food, whereas one fed dry food must drink more to compensate (WSAVA, 2021). The cat is a special case, being a naturally low drinker as a legacy of its desert-dwelling ancestors, which is one of the strongest arguments for including wet food or adopting [mixed feeding](/glossary/mixed-feeding) to support feline urinary health. Practically, clean fresh water should always be available, and a useful behavioural detail is that some cats prefer moving water, which is why drinking fountains can meaningfully increase how much they take in. Monitoring drinking is also a quiet diagnostic tool. Abnormally high consumption, known as polydipsia, can signal underlying disease and warrants veterinary attention; in dogs, intake exceeding roughly 100 ml per kilogram of body weight per day is generally considered excessive (veterinary reference threshold). A sudden change in drinking habits deserves attention even before other signs appear, since it can be among the earliest clues to conditions such as kidney disease or diabetes. Hydration therefore is central to sensible feeding rather than being an afterthought to the [ration](/glossary/ration). For more, see the [Petipedia glossary](/glossary).

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General documentary information. For an individual animal, a veterinarian's advice takes precedence over any online content.