Get

In Your Inbox

Catster is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

Miralax for Cats: Our Vet Explains Dosages, Uses & Side Effects

Share

Infusion of liquid medicine by a veterinarian from a syringe into the mouth of cat

You may notice your cat in the litter box, straining to defecate and being unable to. You may also notice that your cat is only passing small, firm “fecal balls”, vomiting, or just otherwise not acting like themselves. Constipation can occur for many reasons in cats, with various treatments available. A simple over the counter (OTC) treatment you can try is Miralax for cats. This can be effective for both simple cases of constipation, or long-term management. In this article we will discuss more about Miralax, how much Miralax to give a cat, and if there are any side effects you should be aware of. Remember that it is important to consult a vet before giving any medication to your cat.

divider cat faces oct 2024

What Is Miralax?

Miralax is the brand name of an osmotic laxative that contains PEG 3350, or Polyethylene Glycol. Other names include GaviLAX, GlycoLax and ClearLax. It is used to help relieve constipation, or difficulty defecating normally and regularly, often due to firm stools.

What is an osmotic laxative? This means that when swallowed, it travels through the digestive tract (in the intestines), binding to water molecules along the way. This will then cause more fluid to be absorbed into the intestinal tract, increasing the size of the intestines and their water content. As the Miralax and additional water get to the colon, the hope is that the increased hydration of the intestine will cause the hardened stool to soften, therefore making it easier to pass.

Miralax for cats is not a stimulant laxative. A stimulant laxative is a medication that will cause increased contraction(s) of the intestinal tract. It is never recommended to give a stimulant laxative to your cat unless specifically prescribed by your veterinarian.

How Is Miralax Given?

Miralax comes in powder form. It is reported to be odorless and tasteless, though we cannot know for certain if cats and dogs may be able to smell and/or taste it. It does not need any special storage – only to be kept in the container it’s purchased in. Miralax does not need to be kept in the fridge once opened and can remain on your counter or medicine cabinet.

Miralax is taken orally; in other words, it’s eaten. While it does not need to be taken with food to be effective, it is going to be easiest to administer to your cat with food. You can either sprinkle it right on top of their food or mix it in to try and disguise it from suspicious eyes. Of course, you can try to mix it into liquid and give it to your cat with a syringe, but this will likely not end up going very well.

For mild constipation, it should be given twice daily until the stools have normalized and your cat is defecating normally. If your cat is severely constipated, they may need more aggressive care in the hospital first, and stools maintained with Miralax given once or twice a day.

Dosing Miralax and What Happens If You Miss a Dose

Always double-check dosages with your veterinarian. Miralax for cats dosage starts between 1/8-1/4 teaspoon twice daily. Ask your veterinarian if they want you to give this medication to your cat either once or twice a day.

If you normally give it twice a day, then if you miss a dose, your veterinarian may have you double the dose and give it only once. However, it depends on the severity and cause of the constipation in your cat what your veterinarian may want you to do. Miralax is overall very safe. Missing a dose typically will not cause any adverse effects. If anything, missing a dose may cause your cat’s constipation to persist.

Sometimes cats are so severely constipated that they need to be sedated and have stool manually removed by your veterinarian. They are often then kept in the hospital to receive IV fluids and intensive care before going home on medical management. Miralax may be prescribed to your cat by your veterinarian for long term care. Therefore, dosing may be titrated up or down depending on how your cats do and what is causing their constipation in the first place.

divider 1 paws

Potential Side Effects of Miralax

Overall, Miralax is safe for most cats. In some cases, however, it may not help your cat at all. If this is the case, your cat may start to vomit and/or continue to strain to defecate if you are only giving Miralax and not taking any other steps to help your cat.

Other cats may have increased flatulence or diarrhea if too much is given. If this occurs, you should back down on the dose to once daily and contact your veterinarian about further instructions.

If your cat is constipated from underlying dehydration, giving Miralax or any other osmotic laxative may worsen their dehydration. This is because of what we discussed above in that Miralax will draw more liquid into the intestinal tract. Make sure your cat is not only drinking appropriate amounts of water but is also not dehydrated. Your veterinarian can discuss this with you as some cats drinking excessively will still be chronically dehydrated. We see this commonly when cats have chronic kidney disease.

divider cat faces oct 2024

Frequently Asked Questions

How Long Will Miralax Take to Work?

In mild cases of constipation, you should notice results within about 12 hours. However, if your cat is severely constipated, it may take a few days. At minimum your cat should be passing small pieces of firm stool daily. If more than 2 or 3 days has gone by without any stool being passed, you should seek emergent veterinary care.

alert cat near two litter boxes
Image Credit: victorhugosilvafotograf, Shutterstock

Why Is My Cat Constipated?

Constipation in cats can occur for a number of reasons. Sometimes, it’s just from decreased water intake and/or their diet. Other times constipation can be from chronic kidney disease, hairballs, or previous injury. Your veterinarian will likely want to perform radiographs and bloodwork to try to determine what the cause of your cat’s constipation is, and discuss if this may be the beginning of a chronic issue.

divider 3 paws

Final Thoughts

Constipation can occur for several reasons in cats. In cases of mild constipation, your cat may be able to receive medical management at home, including Miralax. Miralax for cats is an osmotic laxative that helps to soften stool by increasing the water content in the gut. It can be purchased OTC as a powder and sprinkled on top of or mixed into your cat’s food. It may be given once or twice daily, depending on your veterinarian’s recommendations. Dosing can be titrated up or down, with few side effects seen. Management of constipation should always be done with your veterinarian, as prescription food and/or other medications may be needed for long-term control.

See Also:


Featured Image Credit: Zhuravlev Andrey, Shutterstock

Want content like this delivered to you?

Sign Up For Our Newsletter

News, insights, expert advice, and everything cat

* By submitting, you agree to our Terms & Conditions and Privacy & Cookies Policy.




How useful was this post?

Click on a star to rate (you can leave written feedback after clicking submit)

Help us improve Catster for pet parents!

Your feedback really matters.

What did you like about this post? Also how can we improve it?

Join the conversation

4 Responses

    1. Yes Gidget, you can technically use plain, original human MiraLAX (Polyethylene Glycol 3350) for a 12 lb cat, as it is frequently used off-label by veterinarians to treat feline constipation. Because it is a tasteless powder, it mixes easily into wet food.
      However, the absolute most important step is to call your veterinarian before giving it to him. Straining in the litter box can sometimes look exactly like constipation when it is actually a life-threatening urinary blockage, which MiraLAX cannot fix. If your vet confirms it is safe to proceed, they will give you the precise dosage tailored to his medical history, though a standard starting guideline for a cat over 10 lbs is typically 1/4 teaspoon mixed into wet food once or twice daily. Always ensure he has plenty of fresh water available, as MiraLAX works by pulling moisture into the digestive tract to soften the stool!

  1. Very interesting article regarding cat constipation. Thank you so much for the information on miralax as well. !! You’ve been a big help with the information for me and my cat Coca-Cola!

Leave a Reply

You’re very welcome to leave a comment or question. Please know that all comments must meet our community guidelines, and your email address will NOT be published. Let’s have a positive and constructive conversation.


Catster's Digital Magazine is Back!

Vet-approved health & behavior advice

Real cat stories & community features

Life Through Minnie’s Eyes: The Cat Behind the Comics

I used to volunteer at a small local cat shelter called Little Flower Rescue. I had actually met another cat, Sylvia, whom I...

The Original Space Invaders – Why Zero Respect for Personal Boundaries Is a Good Thing

Cats have a reputation for being independent, and in many ways they are. But anyone who has tried to work at a laptop...

How Cats Are Helping to Cure Cancer

When most people think about medical breakthroughs, they picture scientists in laboratories and clinical trials involving human patients. Few would imagine that the...

Ask Dr. Paola – My Cat Loves Eating Grass, But It Makes Her Vomit! (June 29, 2026)

Welcome to our “Ask Dr. Paola” series, where every Monday we bring expert advice straight from Dr. Paola Cuevas (MVZ) to help our...

More related

Why Do Cats Rub Their Face on Things? 6 Vet-Verified Reasons

Cats do all sorts of strange and wonderful things, like racing around your house at 2 a.m. or hiding dead mice under your...

Scottish Fold Siamese Mix: Pictures, Info, Temperament & Traits

Scottish Fold Siamese mix cats are not that common, so there is not much known about them. To learn about this designer cat...

Why Is My Cat Shaking While Purring? 4 Vet-Reviewed Reasons

Purring is the most common sound we hear from cats. No matter their size, all cats purr. Even kittens start purring when they’re...

Get to Know a Cat Guy: Eliot Even Writes Songs About His Cats!

In this great big world of ours, there are two categories of people: Those who like cats and those who don’t. Actually, maybe...

Keep reading

Cat Hierarchies & Social Structures: Based on Science

If you live in a multi-cat household, you might have noticed that some of your cats get along better with each other than with others. Do domestic cats have a social structure, and if so, how are these organized? Are...

Feral cats eating on stone path

What Essential Oils Do Cats Hate – The 7 Worst Options (Vet Reviewed)

It’s generally recommended for cat owners to keep their cats away from essential oils. Essential oils can be extremely harmful to cats because they contain very high concentrations of chemicals that are toxic to them. Most cats aren’t fans of...

black and silver portable speaker beside green leaves

Why Is My Cat Biting Me All of a Sudden? 8 Possible Reasons (Vet Verified)

If you’ve spent any amount of time around cats, you’ve probably experienced how fast they can go from purring in delight to digging their teeth into your unsuspecting hand. But why does my cat randomly bite me? While biting doesn’t...

tabby-cat-biting-the-hand-of-the-owner

Do Cats Need a Cat Tree? Vet Approved Pros, Cons & Considerations

Cats love to be up high and observe everything around them but also enjoy having their own space while they sleep their day away. Cat trees are a common staple in most cat-owning households. Not only do they provide that...

cat on top of a cat tree

Vestibular Disease vs. Stroke in Cats: What’s The Difference? Vet-Approved Insights

Strokes in cats are very rare. The symptoms that cat owners most often associate with a “stroke” in cats result from vestibular disease. However, veterinarians may describe the vestibular disease as a “stroke” to aid the pet parents in understanding...

vet holding burma cat

12 Best Cat Foods in 2026: Vet-Approved Reviews & Guide

Proper nutrition is just as essential for your cat as it is for you. Like with humans, a poor diet for cats can lead to issues like malnutrition, weight gain, and certain diseases. It can also have a negative effect...

siamese kitten eating from a stainless bowl

How to Care for an 8- to 12-Week-Old Kitten (Vet-Verified)

Eight to ten weeks old is usually when many breeders and shelters let you take your kitten home, and while they’re certainly adorable at this age, they also have some additional care requirements. It can be a lot to keep...

Inappropriate Elimination In Cats: Vet-Approved Guide & Explanation

Cats usually are pretty good about going to the bathroom in their litter boxes, but some occasionally veer off course and start peeing and pooping in other places. Inappropriate elimination can have various causes, but it’s almost always something to...

cat sitting in a litter box and looking sideways

Love Cats? So Do We! Join the Catster Community

Stay informed with expert pet care insights delivered straight to your inbox! Discover professional guidance on animal behavior, feeding tips, trusted product picks, and much more.




Sign up for the Catster Email Newsletter

Stay informed with expert pet care insights delivered straight to your inbox! Discover professional guidance on animal behavior, feeding tips, trusted product picks, and much more.