This article is all about understanding when to use Miralax for cats’ constipation, and how to give it to them safely. We will look at the side effects to watch out for, and when to stop using it and go back to the veterinarian.
How Often Should Cats Poop?
The general consensus is that cats poop, on average, once a day. However, there is plenty of room for healthy variation. This may be due to age, diet, or simply the fact that all cats are unique.
In fact, attempting to monitor the frequency of your cat’s bowel movements is rarely the most effective way of telling whether they’re constipated. For example, outdoor cats might do poops that you don’t observe. And indoor cats might only manage to partly evacuate their bowels during a toilet trip, so that unpassed feces continue accumulating in their bowel.
So vets also look for any of the following clinical signs of constipation:
- frequent unsuccessful trips to the toilet
- loss of appetite
- vomiting
- weight loss
- lack of energy
- and poor coat condition.
How Do You Unconstipate A Cat?
The best treatment for cat constipation depends upon why they’re suffering in the first place.
Megacolon
Some research suggests that most cats (around two thirds) who experience constipation had pre-existing megacolon. Megacolon is a progressive disorder where the bowel is too large. Because of this, the muscles in the bowel wall don’t work properly. For these felines, constipation is a symptom of an underlying structural problem.
Blockages
The next most common cause of constipation is a tumor or healed injury ‘blocking the exit’, so to speak. These cats need the obstruction to be removed in order to achieve normal bowel movements again.
Less Common Causes
Still further, less common causes of cat constipation include:
- dehydration
- unwillingness to use their litter box because it is dirty, being shared by another cat, etc
- loss of nervous control over the bowel
- and side effects of medication.
Your cat’s vet is best placed to determine why they are constipated. Then they will recommend a course of treatment which solves the underlying problem if possible, and shifts the existing blockage. This might involve laxatives, an enema or a new diet. And very occasionally it may involve surgery to empty or remove the affected section of bowel.
What Laxatives Are Safe For Cats?
Several prescription and over the counter laxatives are considered safe for cats. But none of them should be used without a vet’s say-so.
For a long time, Lactulose has probably been the best known laxative used for cats. Your cat might also have been prescribed the active ingredient in Miralax under its generic name PEG 3350, before it was available over the counter. These days, Miralax is one of the most commonly recommended laxatives for cats. This is because it is easy to administer, and almost completely flavorless.
How To Use Miralax For Cats
Miralax is sold as a water soluble powder, either in a tub, or single dose (for humans!) sachets. The powder can be dissolved in your cat’s drinking water, or a wet food meal. Adding Miralax to your cat’s food is usually a more reliable way to ensure they consume the right dose, since cats rarely empty their water bowl.
If your constipated cat has lost their appetite, you can try adding Miralax to a warm broth instead of plain water. For some cases of cat constipation, your vet might prefer to admit them as an inpatient. They can then administer Miralax via a nasal drip. This is a good way to make sure they receive the correct does promptly, and monitor their response to it.
How Does Miralax Work In Cats?
The active ingredient in Miralax is polyethylene glycol 3350, or PEG 3350. PEG 3350 is hydrophilic which means it attracts and bonds water molecules. One molecule of PEG can bind up to 100 molecules of water!
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When cats take Miralax it binds to water in the gut and stops that water being absorbed out of the intestine. This makes their poop larger, and softer. The increase in volume stimulates the muscles in the bowel to contract and start moving their contents normally again. And being softer, it is more easily passed.
Miralax Dosage For Cats
So, how much Miralax for a cat to achieve this relief?
Your vet will recommend how much Miralax to add to your cat’s meals, how often, and how long for. They’ll base their recommendation on factors like how severely constipated your cat is. And how far their stools are from the “optimum” consistency.
Vets report that the effective dose varies widely from cat to cat, so individualised dosing is essential. As a general guide, cats only need about ⅛ to ¼ of a teaspoon of Miralax, twice a day. This is much less than the contents of a ‘single dose’ sachet. Those sachets contain single doses for humans!
How Long Does It Take For Miralax To Work In Cats?
This can vary a lot, from a couple of hours to a few days. Most cat owners notice their cat experiencing some relief within 6-12 hours of their first dose of Miralax. One study found that the average time taken for Miralax to take effect in cats receiving it via nasal drip was eight hours.
Can I Give My Cat Miralax Daily?
Your vet will advise the correct course of treatment for your pet. They may recommend Miralax daily for just a few days, or a few weeks. Do not give your cat Miralax every day without your vets approval. Or for more days than they advise.
In humans, we know that Miralax can be habit forming. And in cats, vets accept that continuous treatment of constipation caused by megacolon using laxatives gradually loses its effectiveness. Remember – that is most cases of cat constipation.
Which is why it’s so important to see a vet, and establish why your cat is constipated in the first place. Because tackling the underlying cause is the only way to permanently solve the problem.
If your cat has chronic, or long term constipation, your vet might recommend a combination approaches. This could include frequent laxatives, drugs to stimulate muscle function in the gut, and a specialist high fiber diet.
How Can I Get Miralax For Cats?
The Miralax cats take is the same Miralax widely available over the counter at pharmacies and grocery stores. If your vet recommends it, you’ll be able to go and pick it up yourself, without a prescription. You can then administer it to your cat at home, with their normal meal.
Is Miralax Safe For Cats?
Miralax is safe for cats provided it is only used in accordance with a vet’s instructions. It can’t solve constipation where the volume of retained poop is too much to expel normally. If this happens, your vet might recommend manually removing the blockage under general anaesthetic.
Side Effects Of Miralax In Cats
Miralax works by binding water in the gut. This stops it being absorbed through the gut wall into the rest of the body. Due to this, Miralax can cause or exacerbate dehydration. So cats taking Miralax should be encouraged to drink plenty of fresh water
Good ways of doing this include adding tasty, cat-safe meat or fish broths to their wet food. Or using a drinking fountain (since cats are generally unimpressed by standing water).
Like any laxative, a large dose of Miralax can also go a little too far, and cause diarrhea. Call your vet if you believe your cat is experiencing any side effects from taking Miralax. (Besides the pleasant relief of finally being able to use the litter box!)
Miralax For Cats
Used correctly under veterinary supervision, Miralax for cats is a safe, effective and palatable treatment for constipation. Don’t attempt to treat your cat with Miralax without consulting your vet first.
Miralax might be insufficient to treat a large and severely impacted volume of constipation, and administered too frequently it can make a chronic constipation problem worse.
Has Your Cat Ever Needed Miralax?
Did you find it straightforward and effective to use?
Have you got any tips for making it as palatable as possible, and encouraging cats to take on plenty of fluids during treatment?
Let us know in the comments box!
References & Resources
Bracker, Feline Megacolon and Deobstipation, MSPCA-Angell, 2017.
Little, How I Treat Constipation in Cats, World Small Animal Veterinary Association World Congress Proceedings, 2011.
MedlinePlus, Polyethylene Glycol 3350, U.S. National Library of Medicine, 2016.
Tam, Safety and palatability of polyethylene glycol 3350 as an oral laxative in cats, Journal of Feline Medicine and Surgery, 2011.
Yam, Decision making in the clinical management of constipation in the cat, Companion Animal Practice, 2015.
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Miralax was very effective at first but now seems not to be helping. Will check with the vet on next visit.
I’ve had great success with Miralax for my 15 year old cat. His stools were rock hard and few and far between, as he would strain so hard he would make himself sick and throw up every day because he had no room in his bowel. I feed him Friskys wet food in the morning and Blue Buffalo dry food during the day. I’ve always mixed his wet food with warm water and stirred it well. At first I followed the routine of 1/4 teaspoon twice a day of the Miralax powder, it worked well after two days and he was able to eliminate his entire bowel. this worked well for a week and i became concerned that might be excessive because the stools were really soft and mushy, so i have cut him down to 1/8 teaspoon one time a day with his morning wet food, so far this is working well and his stools have firmed up, and he has no problem with elimination, he lets me know how much better he feels by his actions and no more vomiting. So far we have been on this treatment for a little over three weeks with no problems. I plan to continue this routine for another two weeks and then give him a break to see how he does with no Miralax. Oh, he is also an indoor cat only, my suspicions are that something in his diet is causing his constipation, but haven’t pinned it down yet
Hi Ron,
Are you still having good outcomes giving your cat Miralax? I just started giving my 19 year-old Miralax 2 days ago and it helped right away. She has been having increasing problems with constipation for about one year. Thank you for sharing your experiences with your cat.
Cathy P.
Probably the dry food contributing to the constipation…..based on experience with my own cat
Thank you for sharing the information and experiences with your cat! I hope the kitty cat is feeling and doing better and great!
I would eliminate the dry food altogether… That is what is causing the issues to begin with… Cats did not really do well with dry food… It’s good food anyway… I add broth to my cats wet food every time she eats. I just boil chicken and keep that broth she can also eat some of the chicken.
I have been giving MiraLAX to my 11-year-old cat, though I’m not sure what his exact age is, as he was a homeless young adult when I adopted him. Under my vet’s supervision, I give him gabapentin for the pain of his moderately severe (especially for his age) arthritis in his back and legs. He is a large cat with a long spine. Also, with my vet’s okay, I give him MiraLAX 1/8 tsp daily for the constipation due to his inactivity and difficulty straining because of the arthritis. This medication regimen has made him a happy crazy kitten! I have been giving him the MiraLAX for almost two years. My cats eat dry food plus a fourth of a can of wet food mixed w a good amount of water each day. I mix the MiraLAX in my baby’s wet food (he gets a third of the can; he’s a big-boned, hungry boy but not overweight). I give 1/8 tsp to him daily during times when he’s ingesting a lot of hair. I try to pull it out of his mouth before he swallows it, but I’m certain he ingests some when I’m not around to see. In warmer months, he really only needs 1/8 tsp every other day since he has less hair to bother him. I do brush and comb him, a lot.
With his unusually dense hair, the arthritis, and pain with straining to defecate because of it, I really have no choice but to continue the MiraLAX, long-term. He has had absolutely no adverse side effects, only positive results. I use it very carefully, as should anyone. As well as mixing water in with the wet food, I have a small cat fountain he and the others drink from, and I keep the bathroom tap at a slow drip for them. We must always take the BEST care of our beautiful cats’ precious little bodies!
My cat she has mega colon. And a heart murmur. She’s 10 years old. I need some advice. Her doctor saud she should be put down. Im giving her gabapentin. And poop medication. Today she started throwing up and won’t let me touch her ..
My cat had megacolon and what really helped her was cisapride. She also needed lactulose later on but she did well for a couple years. Cats don’t need to be euthanized for a health condition unless it’s life threatening and painful and can’t be resolved. get another opinion.
How is she doing? Did you try Miralax?
If it’s not too late, I think you should take her to another vet for a second opinion. Maybe the dose could be adjusted or there could be other factors that were overlooked. Some vets push euthanasia, but do not feel intimidated.
MY cat was like this. I got him an enema and the vet put him on Cipraside to stimulate the bowels to contract. I got it at Golden Gate compounding pharmacy for animals and it is microtabs chicken flavor. I feed him this in pill pockets. He was also prescribed lactulose which I mix with his dry food and Fortiflora to flavor it. He gets Miralax twice a day in the juice of wet food. Ask your vet about trying some or all of these things.
I have a 12y/o large cat (about 5.5kg) who started having episodes of constipation in the summer. The first couple of times we went to the vet he had to have a (very expensive) overnight stay and enema. The vet was generally useless at suggesting long-term solutions to prevent this happening again, and we’re happy to keep prescribing me Lactulose at £18/two weeks’ worth! I asked about Miralax after reading extensively about it and the vet tried to put me off (they are very money-grabbing round here) but I’ve given it a try and have had great success. We’ve been keeping a spreadsheet and he is now pretty regular with 1/2 teaspoon twice a day (which seems more than average but 1/4 did nothing and he is bigger than most). Some days he doesn’t go but then he has a very large, soft but fully formed BM.
I’m finding I have to give my cat 1/2 tsp twice a day. He can go days without defecating but acts if he feels okay. If the miralax doesn’t work after a few days I need to give him lactulose by mouth, he hates that and fights me and we both end up with it on both of us! If I mix it with food he won’t touch it. He’s 13 and was a rescue cat. It’s quite worrying, the vet originally suggested the Miralax, I use a store brand and expect it’s the same thing. Any suggestions would be appreciated.
I just want to say that Miralax is not generally available in pharmacies or through your vet in the UK, but you can buy it on Ebay. It is not cheap, around £28 a tub, but lasts forever. I have had 2 elderly cats who have really benefitted from Miralax. It is the only laxative that neither of them reject, and seems to be totally acceptable, where Lactulose is definitely not. My vet is ok with that solution. One tub has lasted over a year, although I don’t use it every day.
I don’t see the brand Miralax either at pharmacies in Ontario but there are plenty of other brands that include the same drug, Peg 3350. The same ones that are available for humans. eBay seems a very expensive way to get it. I only give Lactulose in extreme circumstances, the one I have is chicken flavoured but my cat still hates it, but it is guaranteed to work if the Miralax is not helping. Good luck.
I don’t get if the miralax powder can be put right into wet food without first dilutions with water ?
I just mix it with the wet food, no diluting
This is the second time in two months I have had to take my 17 year old cat to the ER with issues that might all be stemming from constipation. I am waiting for the vet to call back with instructions for using miralax. The gave him an enema 6 1/2 hours ago but he has still only pooped a little bit. He will not ever eat his food if anything is mixed into it so I have no idea how I will get enough miralax into him to make a difference. He also has only eaten one brand of food in one particular flavor – he has always rejected any other food. I don’t know how I will get anything into him.
Try mixing the Miralax with a tiny bit of water ( I did this in a shot glass), Be sure to mix well. Then draw mixture up in a plastic syringe (available at your vet or a pharmacy if you don’t have one) and give orally. Two people make this easier, so a helper is best if you have one…cats don’t really appreciate having the syringe put down their throats!
My cat has been on Miralax for a week recommended by his vet. His poop is small but not hard and he still seems to be straining a bit. But he refuses to use the litter box.
Any suggestions on how to get him back in the litter box?
I’ve been thinking about asking my vet about using Miralax for my 15 yr old Maine Coon who I adopted a few years ago. Apparently she had been attacked by a dog with damage to her hindquarters. I suspect her constipation is due to some nerve damage. She is gaga for Churo treats by Inaba, so I am hoping that combining the Miralax w/ the treats might work… otherwise she drinks very little water and barely eats anything. Lactulose does nothing!