Citrucel and Metamucil are not the same product. Both are bulk-forming fiber supplements used to relieve constipation, but they contain different active ingredients that behave differently in your digestive system. Citrucel uses methylcellulose, a plant-derived soluble fiber, while Metamucil uses psyllium husk, a natural soluble fiber from the seed coat of the Plantago ovata plant. That distinction affects everything from gas and bloating to how each one interacts with other health conditions.
Different Fibers, Different Behavior
The core difference comes down to what happens after you swallow each supplement. Psyllium husk (Metamucil) forms a thick, viscoelastic gel when mixed with water. This gel has “self-healing properties,” meaning it can break apart in your stomach and then reform as it moves through your intestines. That reformed gel slows the transit of food through your gut, which helps absorb excess water and firm up loose stools.
Methylcellulose (Citrucel) also forms a gel, but it behaves differently under the physical forces of digestion. It’s more rigid and less likely to reform after being broken up during digestion. Research shows methylcellulose actually speeds up the time it takes for food to travel from your mouth to your large intestine, while psyllium slows that process down. This is a meaningful practical difference if you’re choosing between the two for a specific digestive issue.
Fiber Content Per Serving
Metamucil delivers more fiber per dose. One teaspoon provides about 3 grams of insoluble fiber and 2 grams of soluble fiber, for a total of roughly 5 grams. Citrucel provides about 2 grams of soluble fiber per tablespoon. If you’re trying to meaningfully increase your daily fiber intake, you’ll get there faster with Metamucil, though both products can be taken multiple times per day.
Gas and Bloating
This is where many people notice the biggest real-world difference. Psyllium is a naturally fermentable fiber, which means gut bacteria break it down and produce gas in the process. Some people tolerate this fine, especially after the first week or two. Others find the bloating uncomfortable enough to quit taking it. Methylcellulose is less fermentable, which is why Citrucel is often marketed as the “less gas” option. If you’ve tried Metamucil and found it made you uncomfortably gassy, Citrucel is a reasonable alternative to try.
Which One Works Better for IBS
The two fibers may suit different types of irritable bowel syndrome. Research suggests methylcellulose could be more helpful for people with IBS and constipation (IBS-C), because it accelerates transit through the gut. Psyllium, on the other hand, may be better suited for people with IBS and diarrhea (IBS-D), because its gel-forming properties slow transit and help solidify stool. This isn’t a hard rule, but it’s a useful starting point if you’re experimenting with fiber supplements to manage IBS symptoms.
Heart Health Claims
Metamucil has one advantage Citrucel can’t match: an FDA-authorized health claim linking psyllium to reduced risk of coronary heart disease. The FDA allows this claim for products containing at least 1.7 grams of soluble fiber from psyllium per serving, with a recommended daily intake of 7 grams or more. The mechanism is cholesterol-related. Psyllium’s gel binds to bile acids in the gut, forcing your liver to pull cholesterol from your blood to make more. Over time, this lowers LDL cholesterol.
Methylcellulose is not included on the FDA’s list of eligible soluble fiber sources for this heart health claim. That doesn’t necessarily mean it has zero effect on cholesterol, but it hasn’t met the evidentiary standard the FDA requires. If lowering cholesterol is part of your reason for taking a fiber supplement, Metamucil is the better-supported choice.
Available Forms
Metamucil comes in a much wider range of products. You’ll find it in flavored and unflavored powders, sugar-free versions, smooth and coarse textures, and several brand extensions. Citrucel is simpler: it’s available as a powder for mixing and as tablets (caplets). Both brands offer sugar-free options, which matter if you’re watching carbohydrate intake or managing blood sugar.
The caplet form of Citrucel can be convenient if you dislike the texture of mixed fiber drinks. Psyllium powder, even in “smooth” versions, tends to thicken quickly in water and can develop a gritty or slimy consistency if you don’t drink it fast. Methylcellulose powder generally mixes more cleanly.
Interactions With Medications
Both products carry the same general caution: bulk-forming fibers can reduce the absorption of other medications you take by mouth. They speed up intestinal transit or physically bind to certain drugs in the gut. Heart medications containing digitalis, the antibiotic nitrofurantoin, and aspirin-type drugs (salicylates) are specifically flagged. The standard recommendation is to take either fiber supplement at least 2 to 3 hours before or after any other medication to avoid this problem. This applies equally to Citrucel and Metamucil.
Choosing Between Them
Your choice depends on what you’re trying to accomplish. If you want a fiber supplement primarily for constipation relief and you’re sensitive to gas and bloating, Citrucel’s methylcellulose is the gentler option. If you want the added benefit of cholesterol reduction, or you’re dealing with loose stools, Metamucil’s psyllium has stronger evidence behind it. For general regularity in someone without a sensitive gut, either one works. Both are considered safe for long-term daily use.
Whichever you choose, start with a low dose and increase gradually over a week or two. Drink a full glass of water with each dose. Bulk-forming fibers work by absorbing water, and without enough fluid, they can make constipation worse rather than better.