Dilated Pupils In Cats

Are Dilated Pupils in Cats Something to Worry About?

Dr. Erin Zepp

Jul 28, 2022

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Have you ever seen your cat’s eyes get wide and very dilated? Do you know what this means? How do you know whether or not pupil dilation is a cause for concern in your cat?

If you’re a new cat owner or you’re still getting to know your feline friend’s body language, you may find yourself wondering what pupil dilation means. In the article below, we’ll walk you through some of the most common causes of dilated pupils in cats and help you better understand when this behavior is something to worry about. 

Everyday Causes

Listed below are everyday causes of dilated pupils in cats:

Play and Pouncing

Play and pouncing are by far the most common causes of dilated pupils in cats. Cats of all ages play, pounce, and pretend to hunt around the home. When they do this, their pupils dilate to let in as much light as possible, just like they would in a real hunting situation.

Low Lighting

Low lighting conditions may also cause pupil dilation in cats. This is yet another normal and very common reason why your cat’s eyes may look wide. If you have the lights turned low in your home, your cat’s eyes will be much more dilated than they are in bright lighting.


Excitement may also cause pupil dilation in some cats. If your cat’s eyes become dilated at dinnertime or when she knows she’s about to get her favorite treat, this is nothing to worry about and is part of her normal response to excitement.

Moderate Causes

Listed below are the moderate causes:

Fear and Anxiety

Fear and anxiety cause a cat’s pupils to dilate naturally. If your cat has been startled by something and her pupils dilate for a short time, this is normal. However, if she is often so frightened and anxious that her pupils are wide, she may need anti-anxiety medication from the vet.


Pain is one of the more common causes of dilated pupils in cats. Even mild pain may cause pupil dilation. Watch your cat for other signs that she may be in pain, such as hiding or aggression, and take her to the vet if you suspect she is hurting.

Serious Causes

Listed below are the serious causes of dilated pupils in cats and these require veterinary care.

High Blood Pressure

High blood pressure can sometimes cause dilated pupils in cats that do not go away for a long while. If you suspect your cat has high blood pressure, she will need to be diagnosed by a vet and may need medication to regulate the problem.

Blindness or Low Vision

If your cat has poor vision or if she is blind in one or both eyes, she will likely have dilated pupils as a result. This is natural for blind cats. However, if the pupil dilation occurs suddenly and your cat seems to be losing vision, this is a sign of a serious health problem and should be checked out by a vet right away.


Glaucoma may occur naturally in older cats, but it can sometimes happen in young cats, too. Cats who have glaucoma may experience dilated pupils for long periods of time. If your cat has glaucoma, she will need to be treated for this condition to preserve her vision.


Brain and ocular cancers may sometimes lead to dilation of a cat’s pupils. If your cat is showing severe signs of cancer along with this symptom, including sudden extreme weight loss or extreme lethargy and weakness, take her to the vet for a complete diagnosis right away.

Brain Injury

Although very uncommon, brain injury can sometimes lead to pupil dilation in cats. If your cat has recently experienced a fall from a large height, an injury from a vehicle, or a fight with a larger animal, brain injury could be the cause of this symptom.

Seek Veterinary Care if Your Cat’s Eyes are Dilated

It’s important to note that serious causes of pupil dilation in cats are much less common than every day and moderate causes. Unless your cat is showing significant signs of illness or a major health problem, there is a stronger chance she is dealing with something from one of the first two lists above instead. Although you can certainly have your cat checked by the vet for her pupil dilation, do not worry too much unless she has other concerning symptoms.

A cat’s eyes change, constrict, and dilate multiple times in a day, and the quick-changing behavior of feline eyes can be alarming to first-time cat owners. By learning which situations cause normal pupil dilation and which do not, you can more easily recognize when your cat may be in need of a vet visit. 

If you do suspect your cat’s pupils are dilating due to a problem, don’t hesitate to call VEG. We have locations all over the country that are open 24/7 and our team is ready to guide you and your pet in the right direction. You can speak directly with an emergency vet who will provide advice on your pet’s condition. Contact VEG today!