Dehydration

Dehydration means the body has lost more fluid — and usually electrolytes with it — than it has taken in. It matters particularly in cats because of their evolutionary history: descended from arid-climate wildcats, domestic cats have a famously low thirst drive and are built to extract most of their water from the bodies of their prey. A cat eating only dry food, drinking little, is doing something its physiology never really planned for.

Because of this, dehydration in cats is very often a signpost to something else. The classic 'drinking and weeing more' of chronic kidney disease, hyperthyroidism and diabetes can tip a cat into a fluid deficit, and any bout of vomiting or diarrhoea drains water fast. In hot weather, or when a cat feels too unwell to drink, the balance tips further. This is why persistent dehydration should never simply be topped up and forgotten — the underlying reason needs to be found.

Owners can check hydration at home with two quick tests. Gently lift the loose skin over the shoulders and let go: in a well-hydrated cat it snaps back at once, while in a dehydrated one it sinks back slowly. Feel the gums, too — they should be slippery and moist, not tacky or dry. Prevention leans heavily on diet and presentation: wet food dramatically raises daily water intake, and many cats drink more from a fountain, from wide bowls that do not brush their whiskers, or from stations kept well away from their food and litter. Any cat that is dehydrated and also off its food, vomiting, or known to have kidney or thyroid disease should be seen promptly, as it may need fluids given under the skin or into a vein.