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4 Best Fiber Supplement for Cats With Diarrhea

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Diarrhea isn’t pleasant for anyone but it’s especially unpleasant when your kitty is having the runs and you have to deal with the odor and cleaning up the litter box.

In this article you’ll learn how to tell if a fiber supplement is appropriate for your cat’s diarrhea, the benefits fiber provides, and some products to discuss further with your veterinarian as well as some frequently asked questions.

What Is Fiber?

In the most simple sense, fiber is derived from plant material and is not digested. But there are two main types of fiber that serve different roles in the body.

1. Insoluble Fiber

Insoluble fiber, or cellulose, can be thought of as roughage plant-type material. If you added water to celery, that’s kind of what insoluble fiber is. Insoluble fiber literally cannot be dispersed in water and cannot be digested or fermented as well by the body. It tends to pass more or less undigested through the gastrointestinal tract.

The effect of insoluble fiber is that it increases the bulk of feces as well as shortening the time it takes for digestive contents to pass through the intestinal tract. Because of this effect, it does alter digestibility of nutrients, since they are passing through the GI tract much faster.

Insoluble fiber is more common in weight management diets, diets designed for diabetes, and for helping kitties to pass hairballs.

2. Soluble Fiber

Soluble fiber, which includes pectins and gums, also comes from parts of plant tissue and is used most often in fiber supplements. But unlike insoluble fiber, soluble fiber can absorb water and form something called a gel. Oats are one form of soluble fiber, so if you think of what happens if you add water to oatmeal, that’s essentially what happens with soluble fiber in the body.

Soluble fiber is typically more fermentable, meaning it can be broken down by bacteria in the digestive tract and converted into nutrients called short chain fatty acids (SCFA’s), which cells in the colon (large intestine) use as a preferred source of energy. Highly fermentable fiber that can be converted into lots of SCFAs are termed prebiotics, because they can help to foster beneficial bacteria in the digestive tract.

Soluble fiber will slow down intestinal transit time. It also helps to curb blood sugar spikes after eating, making it beneficial for diabetes as well. As they do absorb water, soluble fibers can help stools to pass more easily, assisting with constipation.

Does My Cat Need a Fiber Supplement for Diarrhea?

Now that we know what fiber is, but before discussing it further, it’s important to think about whether or not your kitty will benefit from fiber in the first place.

Diarrhea can have a multitude of causes and can originate in different parts of the digestive tract. The underlying cause of the diarrhea as well as where it’s coming from are both important to think about when considering fiber supplementation.

The first question to answer is if your kitty is having a quick onset of the runs or whether this is a chronic issue. Similarly, are you thinking about using fiber to help with a short-term issue or will a fiber supplement be part of a long-term solution?

A recent onset of diarrhea can occur with dietary indiscretion, an intestinal parasite, or another recently acquired illness. Chronic diarrhea may occur for similar reasons if an acute cause isn’t treated. But there are other chronic conditions like inflammatory bowel disease (IBD) to think about too.

Although chronic diarrhea is most often thought of as diarrhea lasting for more than 2-3 weeks, you should seek veterinary care for any cause of diarrhea lasting for more than 24 hours or sooner if other signs of illness are also present.

It’s important with ongoing causes of runny poop to determine what the cause is as best as possible so that a proper treatment can be determined. Supplementing fiber alone may help temporarily or not at all if a bigger primary cause is present.

Now, there is such a thing as fiber-responsive diarrhea, which as it sounds, is diarrhea that responds well to fiber supplementation. A diagnosis of fiber-responsive diarrhea does require a trial of fiber supplementation, but also requires ruling out other prominent causes first so that the proper treatment isn’t missed.

Generally, pets don’t need fiber added to their diet on a regular basis. Certain amounts of fiber are required as part of a nutritional formulation in commercial pet foods following Association of American Feed Control Officials (AAFCO) guidelines.

Any diets that are made at home for cats could have a great deal of variability in fiber content and is one reason why having a board certified veterinary nutritionist help in home diet formulations is an important consideration.

Also Read: Best High Fiber Cat Food

What Are the Benefits of a Fiber Supplement for Cats With Diarrhea?

Now, if you and your veterinarian have determined that fiber is appropriate to add, what are some potential benefits of adding a fiber supplement for diarrhea?

In the right forms, many fiber supplements are easy to add to your cat’s diet. Many come as chews, powders, or capsules designed to be opened with the powder inside sprinkled and mixed with food. Many of them are also flavored to increase the chance your kitty accepts them.

If a diarrhea condition is purely fiber responsive, one great benefit of adding fiber is that the diarrhea should resolve. Often, fiber needs to be continually added to the diet or a higher fiber diet itself needs to be used, but this is still a positive with a natural remedy.

If diarrhea is not purely fiber responsive but has another underlying cause, fiber usually still helps to some degree for reasons we’ll get into in just a minute. But you can’t treat parasites or inflammatory bowel disease (IBD) with just fiber and expect those conditions to resolve. You’ve got to have a good idea of the underlying cause and the scope of treatment options.

Many fiber supplements don’t just contain fiber–they also have other additional ingredients like digestive enzymes and probiotics that support a wider scope of intestinal digestive system health. Probiotics can especially be helpful for cats with diarrhea, as microbial imbalance is often present to some degree.

Also Read: 10 Best Probiotics For Cats

Which Type of Fiber Is Best?

The reality of fiber is that both types provide benefits, but too much of one or the other can have unwanted effects. Most supplements contain psyllium which is a soluble fiber source and some may contain a mix of both.

For many cases of acute diarrhea or when fiber is being supplemented in addition to other therapies for a chronic condition, a mix of fiber as found in many supplements is generally acceptable.

In cases of truly fiber-responsive diarrhea, you may need to work more closely with your veterinarian to help determine what proportion of soluble vs. insoluble fiber is best.

Side Effects of a Fiber Supplement for Cats With Diarrhea

Fiber supplements are generally safe to use, but there are some important considerations, especially if your cat has diabetes, other chronic issues with digestibility, or other conditions.

Soluble fiber absorbs water and generally slows down intestinal transit time. At some point though, too much soluble fiber can absorb too much water, and contribute to diarrhea.

Insoluble fiber generally increases intestinal transit time, so too much insoluble fiber can also lead to diarrhea by moving things through the digestive tract too fast.

Combinations of fiber should also be used carefully with diabetics. Fiber can be very helpful for diabetic cats to help curb hunger, encourage weight loss, and reduce blood sugar spikes after eating. But too much can also lead to low blood sugar levels, which can be dangerous and lead to confusion with insulin dosages.

Psyllium, which is a common form of soluble fiber (as found in Metamucil) can be helpful as a fiber source (see the FAQ section). But there are some cats who rarely will have an allergy to psyllium, which can even be acute and life threatening.

Whenever adding psyllium as a fiber supplement for the first time, always make sure to closely monitor your kitty for signs of concern. This can include signs of itching, restlessness, or difficulty breathing.

Lastly, there is such a thing as just too much fiber. Even if it’s not negatively affecting your cat’s stools by adding too much of one or another, too much fiber can affect the digestion of other nutrients in your cat’s diet. Dietary fiber should generally not exceed 10% of the diet. If it does, absorption of other nutrients may be impacted, leading to other nutritional problems.

Absorption of medications may also be affected, just like nutrients can be, so make sure to discuss appropriate fiber supplementation with your vet, especially if your kitty has another chronic disease condition or is on one or more oral medications.

Also Read: The 7 Best High Protein Low Carb Canned Cat Foods

At a Glance: Top 4 Best Fiber Supplement Products for Cats To Buy

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In the comparison table below, we’ve highlighted some of the most important features of each product. You’ll find more detailed information about each product later in the article

Picked by 31 people today!

Proviable Kits

  • A brand of probiotic favored by many veterinarians
  • Contains 7 strains of beneficial bacteria and 5 billion colony-forming units (CFUs) per probiotic capsule
  • The kits specifically come with a syringe of paste containing kaolin and pectin
Picked by 31 people today!


  • Formulated with a combination of soluble and insoluble fiber
  • Can be used short term or long-term if appropriate benefits are seen
  • Includes other nutritional ingredients to support overall health
Picked by 25 people today!

Vetasyl Fiber Capsules

  • Can be used short term or long term if needed benefits are seen
  • Very cost effective
  • Will last for over 3 months with one capsule used once a day
Picked by 21 people today!

Hairball Aid

  • Contains psyllium husk as well as pumpkin
  • The chews are soft and flavored
  • The psyllium may also help with loose bowel movements

Best Fiber Supplement Products for Cats

Following are four products that can be considered for cats with diarrhea. As a disclaimer, selection of these products is based on the author’s experience, but there are no financial incentives or kickbacks to the author for choosing them. All links are directly to the manufacturers’ websites for more information.

#1 Proviable Kits

Proviable, which is made by Nutramax, is a brand of probiotic favored by many veterinarians. Proviable contains 7 strains of beneficial bacteria and 5 billion colony-forming units (CFUs) per probiotic capsule. While the capsules can be purchased on their own for long-term use, the kits specifically come with a syringe of paste containing kaolin and pectin (a soluble fiber) that helps with cases of diarrhea.

The fiber paste can be very effective but is typically only designed to be used consistently for up to 3 days. One downside is that it is most effective if given directly by mouth, which some kitties may be opposed to.

Proviable also comes in the Proviable Forte form, which is available only through veterinarians. Forte has double the number of CFUs per capsule at 10 billion, but the soluble fiber portion is otherwise the same.

#2 Glandex

Glandex, which is made by Vetnique, is formulated with a combination of soluble and insoluble fiber focused on firming up stools to help the anal gland sacs express more regularly. Glandex can be used short term or long-term if appropriate benefits are seen.

Glandex is one of the supplements that also includes other nutritional ingredients to support overall health including omega fatty acids, probiotics, and digestive enzymes.

Glandex has a tuna flavor for palatability and comes in both a soft chew as well as a powder form, providing some flexible dosing options.

#3 Vetasyl Fiber Capsules

Vetasyl, which is manufactured by Virbac, is a psyllium supplement and predominantly soluble fiber. These can be used short term or long term if needed benefits are seen.

The capsules contain powder and are designed to be opened with the powder sprinkled and mixed with food. The barley malt flavor aids in palatability.

One large benefit to Vetasyl capsules is that they are very cost effective. One 100 capsule count bottle generally retails for between $30-$35. For most cats, this will last for over 3 months with one capsule used once a day. For smaller cats under 8 pounds, only ½ capsule is needed, potentially doubling the length of use.

#4 Hairball Aid

Hairball Aid, which is manufactured by NaturVet, contains psyllium husk as well as pumpkin. While the main focus is to prevent hairballs, the psyllium may also help with loose bowel movements as well. The chews are soft and flavored, providing an option to supplement fiber by way of a treat for your kitty.

One downside to Hairball Aid is that the chews cannot be easily mixed with food and two are recommended per day.

Can I Give My Cat Canned Pumpkin for Diarrhea?

It’s an age old question that had to be included here. The simple answer is yes, you can use canned pumpkin to help with diarrhea. So why consider a fiber supplement or diet instead? Because while pumpkin may help, how much it will help and how much pumpkin it will take to provide benefit can be uncertain.

Pumpkin is a mix of soluble and insoluble fiber. Soluble fiber may be more helpful in acute cases of diarrhea, but some pets may need a certain percentage of both and both are certainly needed for general digestive health.

As detailed in the “Problem with Pumpkin”, an article written by veterinary nutritionist Dr. Lisa Freeman with Tufts University, pumpkin may not contain the correct percentages or proportions of fiber a pet needs.

For chronic conditions that need long term fiber supplementation, Dr. Freeman also points out that even giving a tablespoon with each meal may not provide the right amount of fiber needed, with over two cups of pumpkin needed a day for a kitty to match the fiber content of a high fiber prescription diet.

With two cups of pumpkin a day, you’d surely be asking your kitty if they’d at all like some actual food with their pumpkin. Remember, if there are too many calories (exceeding 10%) in your cat’s diet, it may throw the rest of the diet out of balance.

The other thing to be aware of when it comes to pumpkin, which is also discussed in Dr. Freeman’s article is that it is vital when adding pumpkin to be aware of the product you’re using. Plain low sodium canned pumpkin is what’s being discussed.

But there is also canned pumpkin with salt as well as pumpkin pie filling. The sodium levels may far exceed what is safe for a cat’s diet, and the sugar in pumpkin pie filling may only worsen diarrhea.


Supplementing fiber can be helpful for cats with diarrhea, but may not be the only therapy needed to get a diarrhea condition to resolve. Always make sure to discuss fiber supplementation with your veterinarian, as a particular source of fiber may be recommended or a therapeutic diet may be more beneficial over a fiber supplement.

Frequently Asked Questions

Does Fiber Help Diarrhea in Cats?

Fiber can be helpful for cats experiencing diarrhea, but the underlying cause of diarrhea should always be determined as other treatments may be necessary for a diarrhea condition to resolve or be properly managed long term. 

What Can I Give My Cat to Harden His Stool?

Fiber can help with loose stool in the right proportions. Soluble fiber absorbs water and forms a gel and insoluble fiber can help to add bulk to the stool. But it is also important if your kitty is having soft stool or diarrhea to find out if there is another underlying cause that is unrelated to the fiber content of the diet.

Can I Give My Cat Metamucil for Diarrhea?

Metamucil (psyllium) can be given to cats, but must be the unflavored, unsweetened variety. Anywhere from 1 teaspoon up to 4 teaspoons can be considered daily but it is always best to start low and work up to higher amounts, monitoring stool consistency as you go.

It’s rare, but some cats can have an allergic reaction to psyllium, so it is important to closely monitor your cat for signs of itching, breathing difficulty, and abnormal behavior if supplementing with psyllium for the first time.

Can Lack of Fiber Cause Diarrhea in Cats?

Most pets do not need any fiber to be regularly supplemented in their diet, especially if they are eating a commercial diet meeting AAFCO guidelines that already contains dietary fiber. 

However, it is possible to have a condition called fiber-responsive diarrhea. To diagnose this condition, other common causes of diarrhea must be ruled out and a trial of appropriate fiber proportions is conducted with the response monitored over a couple of weeks. 

What Can I Give My Cat to Stop Diarrhea?

This depends largely on the underlying cause of diarrhea. Mild diarrhea caused by brief dietary indiscretion and lasting less than 24 hours with no other signs of illness may be addressed with a bland diet like boiled chicken and rice coupled with a probiotic and fiber supplement.

However, diarrhea can have many causes including (but not limited to) microbial dysbiosis/bacterial imbalance, inflammatory bowel disease (IBD), intestinal parasites, intestinal cancer, and many others, all of which have different treatment approaches.

Having your cat examined by your veterinarian to determine the cause of diarrhea and most appropriate treatment is the best way to address any cause of acute or chronic diarrhea.

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About Dr. Chris Vanderhoof, DVM, MPH

Dr. Chris Vanderhoof is a 2013 graduate of the Virginia-Maryland College of Veterinary Medicine (VMCVM) at Virginia Tech, where he also earned a Masters in Public Health. He completed a rotating internship with Red Bank Veterinary Hospital in New Jersey and now works as a general practitioner in the Washington D.C. area. Dr. Vanderhoof is also a copywriter specializing in the animal health field and founder of Paramount Animal Health Writing Solutions, which can be found at www.animalhealthcopywriter.com. Dr. Vanderhoof lives in the Northern Virginia area with his family, including 3 cats.