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How Long Can Cats Go Without Water? Risks Of Dehydration

If your cat's not drinking normally, it could be an emergency. Here's some information to help you know when to call the vet.

MJ Shaffer writer with Dog

Last Updated: August 11, 2022 | 6 min read

Thirsty cat sitting in front of a emty water dish and looking up to the camera

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One of the first animal-related Quiz Bowl questions every 4-H kid learns to answer is this: what is the most important nutrient? The answer is water. If an animal (or a human) doesn’t get sufficient water, all the other nutrients become moot. Cats’ bodies are sixty to seventy percent water, and fresh, clean water should be available to them at all times. When cats don’t drink enough water, they’re susceptible to many health problems.

How much a cat needs to drink to stay healthy depends on several factors. Age, health condition, and environmental temperature can all make a cat need to drink more water than usual. Even the type of food he eats may make a difference in how much water he needs to drink.

Sometimes, cats don’t drink as much water as they should to stay healthy. There are a few common reasons why and also strategies to get your companion to drink more. You’ll need to know how to tell if he’s getting dehydrated. If he’s not drinking enough water for more than a day or two, he’ll need to be seen by your veterinarian.

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Why Water?

Every function in a cat’s body is based on water. Water is necessary to regulate body temperature, maintain proper electrolyte balance, digest food, lubricate joints, and deliver oxygen and nutrients to the organs in the body. If cats aren’t adequately hydrated, these functions can break down.

Cats need roughly four ounces of water per five pounds of lean body weight. So a ten-pound cat needs around eight ounces, or one cup, of water each day. Water doesn’t leave the body only through urination. Even the humidity in exhaled breath is water lost. When water loss increases, water intake needs to increase at a corresponding rate to maintain stasis. If a cat goes three days without water, he may be in crisis.

Health Problems Caused By Dehydration

When a cat becomes dehydrated, all the body functions that require water begin to work suboptimally even before they fail. If a cat doesn’t drink enough water, he’s more likely to develop urinary stones. The kidneys aren’t able to flush toxins from the body. If we don’t remedy the situation, they begin to lose circulation, and organ function is compromised. They lose the ability to regulate their body temperature. They may develop heart arrhythmia. Eventually, neurological problems ensue.

If your cat is not getting enough water, you’ll be able to notice some visible symptoms. He’ll become sluggish and lethargic. His appetite may suffer, and he may weaken. As his dehydration worsens, his eyes may appear sunken in their sockets. His skin will lose elasticity, and if you gently pinch his skin where it is loose over his shoulders to form a tent, it will remain tented and only slowly go back to normal. In an adequately hydrated cat, the skin should immediately slip back to normal. To begin with, senior cats may have skin with less elasticity, so consider that.

Health Problems That Cause Dehydration

Thirsty longhair cat drinking water from a pet drinking fountain
There are a number of health risks associated with a cat who is dehydrated.

Ironically, some things that can happen when a cat becomes dehydrated can also make him less likely to drink enough water. You’ll have to determine which came first, not drinking or him feeling poorly. Your cat may be caught in a downward cycle. Cats may not drink enough if they’re weakened or have appetite loss from illness. If their teeth hurt from dental problems, they’ll avoid drinking. If they have limited access to water indoors or out due to a lack of water sources or territorial issues, they won’t have the opportunity to drink as they should. Sometimes, a disease causes dehydration as a byproduct of its effect on the body.

Chronic Kidney Disease

Chronic kidney disease (CKD) is mainly a problem in older cats. Generally, by the time symptoms of kidney failure develop, the damage has been happening for months or even years. Some early signs of kidney failure like poor haircoat and weight loss mirror what can occur naturally with aging. With CKD, the kidneys filter less efficiently. Cats produce more urine, and it is more dilute. Cats usually drink more to compensate for the increased fluid loss.

If diagnosed early enough, you can manage the disease with special diets, phosphate binders, antibiotics, potassium supplementation, vitamins B and C, anti-vomiting medications, drugs to lower blood pressure, and drugs to initiate the production of red blood cells. Properly managed, kidney disease progresses slowly, and you may have many more years with your best friend.

Diabetes

Diabetes is characterized by the body producing an insufficient amount of insulin or not adequately responding to the insulin available, or both. Glucose in the bloodstream becomes dangerously high and ends up in the urine. The kidneys won’t retain water normally, and your cat will produce excessive amounts of urine. To compensate, he’ll drink excessively. Because diabetic cats can’t use blood glucose for energy, they lose weight and muscle mass. See your veterinarian if your cat shows excessive urination and thirst symptoms. The test for diabetes is straightforward, and you can discuss treatment options.

Unfortunately, cats with Type II diabetes won’t get better from dietary changes alone. They need insulin injections. Insulin combined with a diabetic-specific diet will allow your cat to live a relatively normal life. Although damaged kidneys don’t heal, the goal of treatment is to maintain a blood glucose level to eliminate the symptoms of diabetes, namely excessive drinking, urination, and weight loss.

Vomiting

If your cat is vomiting, he’s losing fluids. A cat will vomit on occasion for any number of reasons, but if he’s vomiting more than once a week or has other symptoms, call the vet to determine the cause and get supportive care. Depending on the diagnosis, your cat may need fluids subcutaneously or intravenously to support him as he recovers.

Diarrhea

Feline diarrhea may be self-resolving or could be a symptom of a more severe problem. Diarrhea causes ingested food and water to move too quickly through the cat’s digestive system. It can cause an imbalance of electrolytes and insufficient absorption of nutrients and water. If your cat’s diarrhea lasts more than a couple of days with no apparent cause like a change in food, or there is concurrent lethargy, loss of appetite, or lethargy, see your veterinarian to rule out a more serious issue.

Hyperthyroidism

We hear more about hypothyroidism, but hyperthyroidism is common in older cats. The thyroid gland overproduces thyroid hormone, which increases metabolism. The most common symptom is weight loss despite increased appetite. Increased thirst and water intake cause increased urination. Eventually, the cat will look unthrifty and act restless and out of sorts. Although the cause is unknown, there may be a connection to dietary iodine. Your vet can test your cat’s thyroid levels, and if they suggest hyperthyroidism, determine the best course of treatment. Treatments include surgery, oral medication, radioactive iodine, or a prescription diet with very low iodine.

Medications

If your cat is on medication, he may appear more thirsty than usual (you can fill his water bowl with a measuring cup and monitor daily intake so you can give your veterinarian accurate information); touch base with your veterinarian to see if this is a normal side effect. Medications such as diuretics, steroids, and some anti-seizure drugs will make your cat more thirsty, and he’ll drink more water. Some medicines, like Metacam, could cause kidney failure as a side effect, so if you see increased thirst, consult your veterinarian immediately for further instructions.

How To Increase A Cat’s Water Intake

If you want to ensure your cat is drinking enough water, keep it fresh. Some cats even prefer running water to still so that special drinking fountains will make pique their interest. If you’re a multiple cat family, ensure the water dish isn’t in “territory” claimed by your dominant cat. Your cats need access, so numerous bowls of water in different parts of your home may be necessary. Feeding wet food or adding a little water to his food can increase his water intake, but only if it doesn’t make the food unpalatable to him. Adding a bit of tuna or canned food juice to the water may make it more appealing to him, but be sure to change your water frequently and thoroughly wash any film from his bowl so bacteria doesn’t grow.

Final Thoughts

Healthy cats in typical household situations can only go three to four days without water before beginning to experience systemic failures due to dehydration. Animals can go much longer without food, close to two weeks, than they can without water. Extreme heat can shorten this period for outdoor cats, so be sure there’s clean, cool water available. Be sure they have shade to which to retreat when the temperatures soar. In frigid weather, be sure the water you provide for your outdoor cats doesn’t freeze.

Because cats can go for such a short period of time without water before having serious health problems, make sure you check their water source daily. If you go on vacation and leave your pets home, be sure your pet sitter knows the locations of all the bowls to clean and refill. If your cat stops drinking or is losing fluids from vomiting or diarrhea, consult your veterinarian. Don’t take a wait-and-see attitude when it comes to dehydration. Remember, three days can be the difference between life and death.

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