Why Cats Sleep With Their Eyes Half Shut

Cats do some pretty weird things. If you share your home with one, you could probably list a few. Sometimes, their behaviors give their owners a good chuckle, like when they sleep in cardboard boxes, lie on newspapers or magazines, or walk sideways to look tough. Some cats sit on anything you're using, too, like your laptop. Other feline behaviors could be considered a little creepy, like sleeping with their eyes partially open. Cuteness spoke with Dr. Matt McGlasson, an Instagram internet-famous veterinarian coined as "The World's #1 Cat Vet," about the behavior. He said it likely stems from pre-domestication days.

Perhaps you've seen your cat sleeping this way and got a little freaked out by seeing its eyes that way. The good news is, it's typically considered a normal occurrence during sleep, as long as you don't see swelling or discharge, and your cat doesn't repeatedly paw at its eyes. Swelling, excessive pawing, and eye discharge in cats could indicate an injury or other problem, so you'd want to schedule a visit with your vet if you notice any of these conditions. However, even without these extra conditions, you might still be concerned about the behavior and wonder about your cat's sleep quality. Dr. McGlasson, a cat parent himself, shared some reassuring insight on this specific question as well.

Even if cats could speak, they probably wouldn't be able to tell us exactly why they sleep with their eyes half shut, so veterinarians can't give a definitive explanation either, but Dr. Matt McGlasson shared exclusively with Cuteness his two cents. "Sometimes, when a cat is not in a deep sleep, their eyes will be slightly open. This is thought to be an evolutionary trait that might help them stay alert of danger," he said. So basically, if a cat's eyes are partially open, it indicates that it's not fully asleep.

He added that a cat's third eyelid, called the nictitating membrane, "offers additional protection for their eyes." It also helps moisten the mucous membrane. This eyelid is typically a grayish-white color or pale pink. Dr. McGlasson noted when you might see it: "Sometimes, when your cat is tired, you may see this third eyelid peeking up from the corner of their eye," he said. If you see this membrane while your cat is awake, however, call your vet, as this may be a sign of a medical condition.

Domesticated cats obviously don't have full-time jobs and other responsibilities like their humans do. They don't have a long to-do list that could cut into their night-time sleep schedule. They can sleep whenever they want, day or night, especially if they're indoor cats that are home alone for a portion of the day. Even though some cats sleep with their eyes partially open at times, they still have hours and hours left of the day to get plenty of deep sleep — including sleeping right next to you.

During Dr. Matt McGlasson's interview with Cuteness, we asked about the effect that sleeping with partially opened eyes has on a cat's sleep quality. "Typically when they are in full sleep, their eyes will close fully," said Dr. McGlasson, "but don't worry; cats are great at getting plenty of sleep. The average cat sleeps 12-16 hours a day!" 

If you're concerned about your cat's comfort or want to make it feel safer in your home, you have options to make changes in these areas. "Cats need a safe space to rest where they feel secure," Dr. McGlasson said. "Sometimes, a cat tree or place for them to perch up high is required if you have a nervous cat. But if your cat is completely comfortable in your home, they can sleep almost anywhere! Cardboard boxes are my cat's favorites." With this knowledge of our cats, we can all sleep a little easier with our eyes fully closed.