Dehydration

Dehydration occurs when a cat loses more water than it takes in. Common causes are vomiting, diarrhea, fever, not eating or drinking, and diseases that make the body lose water, such as chronic kidney disease, diabetes mellitus and hyperthyroidism. Cats from desert ancestors drink little and get much of their water from food, so a cat on dry food only, or an ill cat, can slip into dehydration easily.

Signs include lethargy, dull and sunken eyes, dry or tacky gums, a dry mouth, loss of appetite, constipation and, in severe cases, a fast heartbeat and collapse. A skin tent test, in which loose skin between the shoulders is lifted and slow to fall back, is often described online. It is unreliable, particularly in thin or older cats, and a vet should judge hydration instead.

A cat that vomits repeatedly, has diarrhea, is not drinking, or seems weak should be seen by a vet, because dehydration can be a sign of a serious illness and a cause of further harm. The vet may run blood tests and give fluids by drip or under the skin, depending on how severe it is. Do not try to force water into a cat. Ask your vet how to encourage a cat to drink and whether wet food, fountains or extra bowls would suit yours.