June 30, 2025, 2:07 pm | Read time: 4 minutes
You often read that cats can drink saltwater. But how does that fit together? After all, cats have rather sensitive kidneys and generally aren’t fond of drinking. PETBOOK editor and biologist Saskia Schneider has explored this question and explains why salt in water can even have positive effects for cats.
Even as children, we learn that drinking saltwater is not a good idea—even if you’re very thirsty. The salt in the water is so highly concentrated that it only dehydrates the body further. This applies not only to humans but also to animals. Only a few have developed special mechanisms that allow them to drink saltwater without losing water. These include seabirds like gulls. You wouldn’t expect this ability in cats, given their sensitive kidneys. Yet, you occasionally hear claims that cats can drink saltwater. So, what’s the truth?
Can Cats Drink Saltwater? Here’s What Research Says
As incredible as it may sound to cat owners, science has long known that cats can drink saltwater. A study published in 1959 in the “American Journal of Physiology” demonstrated that cats can drink seawater without becoming dehydrated: “Under certain conditions, where food provides sufficient calories but not enough water for a dehydrated cat, these animals are proven to rely on seawater intake. They generally drink enough seawater […] to thrive and even compensate for a previously caused water deficit,” the study’s summary states.
But how do cats manage not to lose more water from saltwater? The secret lies in their kidneys, which are often considered a weak point for these animals. In fact, this organ in cats can excrete excess sodium, or salt, allowing saltwater to hydrate them. This ability likely traces back to the cat’s origins as a desert and steppe dweller. Water was scarce there, which is one reason cats are naturally poor drinkers. They meet their fluid needs primarily through their food. The cat’s kidneys are very efficient at filtering high salt levels from food, enabling cats to drink saltwater in emergencies.1
Cats Can Tolerate Four Times the Salt Levels Humans Can
While this ability has its limits, theoretically, cats could meet their entire fluid needs with seawater for one or two days. A five-kilogram cat needs about 250 milliliters of water. This amount of seawater contains about 8.75 grams of salt. Since the lethal dose is about four grams of salt per kilogram of body weight, the cat would survive. In comparison, for humans, a dose of 0.5 to 1 gram of table salt per kilogram of body weight is considered lethal. Cats can tolerate four times the amount of salt. 2
Salt Can Have Positive Effects for Cats
Several studies have shown that salt in cat food can even have positive effects. They examined how increased salt content (sodium chloride) in food affects cat health. The results showed that salty food causes cats to drink more and urinate more. This is particularly beneficial for animals prone to urinary tract diseases, as increased drinking and urination help flush out harmful substances.
A common concern was that too much salt might damage the kidneys or heart. However, long-term studies with healthy, even older cats show that no harmful effects on blood pressure, kidney function, or heart were observed over the years. Even in cats with slightly elevated creatinine levels at the start of the studies, no negative effects occurred. The data suggest that salty food is safe for healthy cats—but caution is still advised for existing kidney disease. 3, 4, 5
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Should I Add Salt to My Cat’s Drinking Water?
Even though cats can drink saltwater without harm and salt in food can have positive effects, you should refrain from adding salt to your cat’s water or food. The ability to drink saltwater is a survival strategy, not a preference. Even though cats can tolerate high salt levels, it stresses their organs and should remain an absolute exception. Still, it’s good to know you don’t need to rush to the emergency room if your cat takes a few sips from a saltwater pool or nibbles on salty ham.
A proper diet and fresh, clean tap water are enough to keep your cat healthy. Since some animals are poor drinkers, it might make sense to offer meat broth instead of water—but please, without salt. There are also special cat soups or drinks, which are especially useful for cats that eat only dry food.
We have compiled more tips on how to get cats to drink more water here for you.