The 5 Best Fiber Supplements for Diarrhea

It doesn't make for good conversation, but if you're running to the bathroom a little more often than usual, then it's time to do something about your diarrhea.

Lucky for you, if it's not chronic and you don't have any other gastrointestinal conditions, getting your diarrhea under control may only require a slight change to your diet or an added fiber supplement to cut back on your frequent trips to the loo.

But wait, doesn't fiber treat constipation? Does fiber help with diarrhea, too? The answer is yes to both, which is why the type of fiber and how much you take really matters. (For example, products like Citrucel and FiberCon are bulk-forming laxatives meant to treat constipation, not diarrhea.)

Psyllium husk is the best fiber supplement for loose stools, says registered dietitian Chelsea Macias, RDN. That's because it's a form of soluble fiber, which slows down digestion and helps bulk up your stool, according to the Linus Pauling Institute. (By contrast, insoluble fiber speeds up digestion, which could make diarrhea worse.)

Indeed, psyllium turns into a gel in your intestines, which can help firm up loose or liquid stools, according to a 2021 review of the research in ​Nutrition Today​. Another review, published September 2017 in the ​International Journal of Molecular Medicine​, says psyllium is both safe and effective as a fiber supplement for IBS with diarrhea (although you should talk to your doctor first if you have irritable bowel syndrome).

But that doesn't mean you should load up on fiber, as that might be too tough on your digestive system (which is already dealing with a lot) and could even lead to constipation. Rather, stick to a low dose: about 3 to 5 grams.

With that in mind, here are the best fiber supplements for diarrhea.

We tapped a registered dietitian for her recommendations on what to look for and chose our top picks based on the following criteria:

• Ingredients
• Quality and Safety
• Cost
• Availability

Yerba Prima gets the best overall nod among stool-hardening supplements because it checks three important boxes: type of fiber, cost and quality. No fanciness or frills means you get the best bang for your buck.

One serving provides 4.5 grams of fiber (3.5 grams of soluble fiber), so consider starting with a half dose. Then keep this on hand for any fiber supplementation after your symptoms resolve.

Consumer Lab, a third-party testing lab that checks for potency and purity of dietary supplements, gives this supplement a thumbs up for quality. It's also certified USDA organic, which ensures you aren't getting any additives you don't want.

Metamucil has been a long-time favorite psyllium supplement. This comes in a powdered form and is easy to mix into your favorite drinks or yogurt.

Its orange flavor is more pleasing to the palate than many other supplements, but that taste comes at a cost. The stevia in this product may cause nausea or stomach upset in some people, and others may not like the aftertaste. Metamucil also makes a fiber supplement with sugar ($13.59, Amazon.com), but keep in mind that it delivers 8 grams of added sugar per serving (about a third of the recommended daily amount, per the American Heart Association).

Metamucil says the serving size is 1 to 2 teaspoons for its stevia-sweetened product, but it's recommended you start out with 1 teaspoon (3 grams of fiber) if you've never taken fiber before.

Metamucil also makes orange-flavored fiber gummies, but these contain a soluble fiber called inulin rather than psyllium, so they're not a good choice when you have diarrhea.

These fiber pills for diarrhea contain 3.3 grams of psyllium fiber per serving, which is a good amount when you're treating diarrhea. It's recommended you take the capsules with a full 8 ounces of water.

NOW Foods adheres to current good manufacturing practices (cGMPs), which is a quality control program set by the Food and Drug Administration (FDA). NOW psyllium husk capsules passed Consumer Lab's test for quality and heavy metals, making this a safe choice.

The suggested usage is to take three capsules, three times a day, but stick with once a day until your diarrhea symptoms have resolved.

NOW Foods gets another nod for a quality psyllium powder supplement. This powder is finely ground, making it ideal to mix into your drinks or bake into your favorite dishes.

One serving has a large amount of fiber, 7 grams per tablespoon, so it's best to start out with a half tablespoon or even a teaspoon when you start taking this fiber.

It's an inexpensive choice and one you can continue to use long after your diarrhea symptoms are gone. It also has thousands of 5-star reviews on Amazon.

While you may not have heard of Organic India, they make a whole husk psyllium fiber that has been tested and approved for quality and safety by Consumer Lab.

One serving provides 4 grams of soluble fiber, which is right in the sweet spot, but you could still take a half tablespoon starting out to ensure your body reacts well.

It is certified organic, which is another measure of strict quality standards. It also doesn't have any additives, added sugar or artificial sugars — just psyllium.

To recap what we discussed above, a fiber supplement to treat diarrhea should check the following boxes:

This type of fiber has been shown to help slow digestion and firm up loose stools.

You don't want to overdo it on fiber when you have diarrhea, so stick to a dose between 3 and 5 grams.

A supplement that has been given the stamp of approval by a third-party tester such as Consumer Lab is more likely to contain the ingredients it claims, in the amount it claims and without any added fillers or harmful substances.

If your diarrhea is not getting better or seems to get worse, take a break from your fiber supplement and call your doctor. Not everyone's body reacts the same way to fiber, and you may need to take a different approach.

These fiber supplements are not recommended for children. If your child has diarrhea, call their pediatrician, who can advise you on how best to treat it.