Dehydration in Cats: Signs, the Skin Test and How to Rehydrate Safely

By Tailwisp Editorial TeamUpdated October 20, 20264 min read

Cats evolved from desert ancestors, and they do not drink much. Even so, they can become dangerously dehydrated, particularly when they are ill, old or very young. Dehydration makes almost every illness worse, and it is often the reason a sick cat needs to go on a drip.

What is dehydration?

The body is about two thirds water, and every organ needs it. When a cat loses fluid through vomiting, diarrhea, fever, heat or increased urination, and does not replace it, the volume of blood falls and tissues dry out. The kidneys, in particular, need good blood flow, so dehydration can cause or worsen kidney damage.

Signs

• Dry, sticky or tacky gums, instead of moist and slippery.
• Sunken eyes, or a visible third eyelid. See third eyelid showing in cats.
• Lethargy and weakness.
• Loss of skin elasticity.
• Reduced appetite.
• Less urine, or dark urine.
• Constipation, or hard stool. See constipation in cats.
• Panting, a fast heartbeat and cold paws in severe cases.
• Collapse.

The skin tent test

Gently lift the loose skin over the shoulder blades and release. In a hydrated cat, it springs back at once. In a dehydrated cat, it returns slowly, or stays in a tent. The test is a rough guide, since thin, old and overweight cats may give misleading results, and a normal result does not rule out dehydration. Use it with gum checks and the overall picture. See how to check your cat's vital signs.

The gum and capillary refill check

Lift the lip and look at the gums. They should be pink and wet. Press a gum with a fingertip to blanch it, and release. Color should return in one to two seconds. Slower return, pale or very dark gums, or tacky texture are warning signs.

Causes

• Vomiting and diarrhea. See cat vomiting causes and diarrhea in cats.
• Kidney disease. See chronic kidney disease in cats.
• Diabetes and hyperthyroidism, which increase urine output. See diabetes in cats and hyperthyroidism in cats.
• Fever and infection.
• Heat exposure. See heatstroke in cats.
• Not drinking, because of pain, nausea, mouth disease or a dirty or unappealing bowl.
• Dry-food-only diets, which supply little moisture. See wet vs dry cat food.
• Blood loss, or burns.

What to do at home

If your cat is bright, mildly dehydrated and able to drink:

• Offer fresh water, and water in several locations.
• Offer wet food, warmed slightly, and add water or low-sodium broth made without onion or garlic. See are onions and garlic toxic to cats.
• Try a fountain. See cat water fountains: worth it.
• Keep the cat cool and calm.
• Call your vet for advice, and do not wait long.

Never force water into the mouth, which can cause aspiration. Do not give sports drinks or human electrolyte products without vet advice.

When to go to the vet

Go to the vet promptly if your cat has sunken eyes, tacky gums, weakness, vomiting, diarrhea for more than a day, or has not drunk for a day. Kittens and seniors should be seen sooner. A cat that is cold, limp or unresponsive needs an emergency clinic. See cat emergency warning signs.

Veterinary treatment

Vets give fluids, either under the skin, in mild cases, or into a vein, for moderate or severe cases. They treat the cause, check bloodwork and monitor the kidneys, electrolytes and blood sugar. Hospitalization may be needed. For chronic conditions such as kidney disease, owners can be taught to give fluids at home. See how to give a cat subcutaneous fluids.

Prevention

• Feed wet food, at least in part. See how to get a cat to drink more water.
• Keep water bowls clean and full, away from litter and food.
• Offer several bowls, and consider glass or ceramic. See how to clean cat food bowls.
• Keep cats cool in hot weather. See keeping cats cool in hot weather.
• Treat illness early.
• Regular senior screening. See senior cat care guide.

Home hydration habits that help

Add a tablespoon or two of warm water to each wet meal, and offer water in different bowl types and places. Some cats like running water, others prefer a glass bowl. Keep the bowls away from the litter box. Measure intake for senior cats, so you notice a change. Small habits protect cats with kidney problems.

When to see a vet

See a vet if you think your cat is dehydrated. Use the US vet directory to find a clinic.

This article is general educational information, not veterinary advice. Every cat is different. If your cat is unwell, or you are unsure about a symptom, diet change or medication, contact your veterinarian.