If you have searched “Citrucel for constipation,” you have probably already tried a few things that did not work, or you are trying to avoid the bloating and grit that come with a psyllium supplement like Metamucil. Citrucel is a long-established, over-the-counter fiber laxative in the United States, and it uses a different type of fiber than most other products on the shelf.
This Citrucel review looks at what is actually in the product, what the clinical evidence says about whether Citrucel helps constipation, how it compares to psyllium-based options, and how to use it safely, including for chronic constipation.
What Is Citrucel?
Citrucel is a brand-name, over-the-counter fiber laxative. Its active ingredient is methylcellulose, a semi-synthetic soluble fiber made by chemically modifying plant cellulose. Citrucel Fiber Therapy is sold in two main forms:
- Caplets: 500 mg of methylcellulose per caplet, taken with a full glass of water.
- Powder: 2 g of methylcellulose per rounded tablespoon, dissolved in water or juice; available in a regular (sweetened) version and a sugar-free, orange-flavored version.
Unlike highly fermentable fibers such as inulin, methylcellulose is not fermented to any meaningful extent by gut bacteria in the colon. This is one reason Citrucel is often marketed as a fiber that is less likely to cause excess gas. It is worth being fair to psyllium here too: psyllium is also relatively well tolerated from a gas standpoint compared with fibers like inulin, so the more accurate way to put it is that Citrucel is a low-fermentation option, not that psyllium itself ferments heavily.
Citrucel Methylcellulose: What It Actually Is
Methylcellulose is derived from plant cellulose and chemically modified so that it disperses in water and forms a viscous gel. It is not digested in the small intestine and acts primarily as a bulk-forming fiber. In summary, it is:
- Citrucel’s active ingredient, methylcellulose, is classified as a soluble fiber; the product label describes it as 100% soluble fiber
- A low-fermentation fiber, unlike more fermentable fibers such as inulin
- Not digested in the small intestine, and reaches the colon largely unchanged
- Also used outside of constipation care, including as an eye lubricant and a food thickener, though the Citrucel product itself is formulated specifically as a laxative
How Does Citrucel Work?
Citrucel works as a bulk-forming laxative. Methylcellulose absorbs and holds water in the intestinal contents, forming a soft, bulky mass that helps increase stool water content and makes stool easier to pass. The added bulk can also help stimulate normal intestinal movement (peristalsis).[6]
Because Citrucel needs to absorb water to work, it must always be taken with a full glass (at least 8 ounces) of water or another liquid. Taken without enough fluid, it may swell before reaching the stomach or intestine and can increase the risk of choking or blockage.
Citrucel generally produces a bowel movement within 12 to 72 hours, so it is slower than a stimulant laxative or an osmotic laxative like MiraLAX, but this is typical for bulk-forming fiber supplements and is not intended for same-day relief.[11]
Does Citrucel Help Constipation? What the Research Shows
The short answer, based on the available evidence, is yes: methylcellulose has been shown to increase stool frequency and improve stool consistency in people with constipation, though the research base specific to methylcellulose is considerably smaller and older than the research on psyllium.
A few specific findings are worth knowing:
- A controlled study of 59 chronically constipated adults tested daily methylcellulose at 1, 2, or 4 g against a comparison group taking 3.4 g of psyllium. Every dose of methylcellulose produced statistically significant increases in stool frequency, stool water content, and fecal solids. The psyllium group also improved. The study was not designed as a head-to-head superiority trial, so it should be read as evidence that both fibers work, not as proof that one works better than the other.[1]
- A 1989 study of 538 patients with constipation found that daily methylcellulose, taken as 1 to 3 tablespoons per day, improved bowel frequency, stool consistency, and ease of passage; 61% of patients were judged to have less constipation after treatment. This was not a modern randomized controlled trial, so its findings are best read alongside newer evidence rather than treated as definitive proof of effectiveness.[2]
- The American Academy of Family Physicians’ patient education resource lists methylcellulose (Citrucel), alongside psyllium (Metamucil) and polycarbophil (FiberCon), as one of the standard bulk-forming laxatives, and notes that bulk-forming laxatives are generally the safest laxative category.[5]
It is worth being precise about the limits of this evidence. A 2022 systematic review and meta-analysis of 16 randomized controlled trials involving 1,251 adults, published in the American Journal of Clinical Nutrition, found that fiber supplementation overall improved constipation, with psyllium among the fiber types showing a significant effect.[4]
The evidence specific to non-psyllium fibers, including methylcellulose, is more limited in this review. In practice, this means methylcellulose is a genuinely evidence-supported option for constipation, but the modern trial base behind it is thinner than the trial base behind psyllium, and direct head-to-head comparisons between the two remain limited.
Citrucel for Chronic Constipation
For chronic constipation specifically (infrequent, hard, or difficult-to-pass stools lasting several weeks or longer), the 2023 joint clinical practice guideline from the American Gastroenterological Association and the American College of Gastroenterology (AGA/ACG) reviewed fiber supplements, including psyllium, methylcellulose, bran, and inulin, as part of its evidence search. Its formal recommendation suggests fiber supplementation over no fiber for chronic idiopathic constipation, citing bran, inulin, and psyllium by name, based on low certainty of evidence, a conditional recommendation.[3]
The guideline included methylcellulose among the fiber interventions it considered, but no eligible randomized controlled trials of methylcellulose were found for its analysis. Among the evaluated fiber supplements, psyllium was the only one with evidence judged sufficient to support effectiveness, although the overall certainty of evidence for fiber supplementation was low.[3]
By comparison, the same guideline gives a strong recommendation to polyethylene glycol (PEG, the ingredient in MiraLAX), based on moderate certainty of evidence, making PEG’s guideline support stronger than methylcellulose’s for chronic idiopathic constipation. For a full breakdown of how fiber stacks up against PEG and other options for chronic use, see our complete guide to OTC laxatives for constipation.
In practical terms, this means methylcellulose can be a reasonable fiber option for some people managing chronic, ongoing constipation, particularly those who prefer a low-fermentation fiber, but the evidence specific to methylcellulose is thinner than the evidence for psyllium, it is not guaranteed to work for everyone, and PEG has the stronger guideline backing for chronic idiopathic constipation. If Citrucel alone is not resolving your symptoms after several weeks of consistent use, our guide to softening stool naturally covers what to add next.
How to Take Citrucel
Always follow the label of the specific product you buy, since dosing varies slightly between the caplet and powder formulations. As a general pattern, based on the current product label:[11]
- Caplets: Adults typically start with 2 caplets, up to 6 times a day, not exceeding 12 caplets in 24 hours, each dose taken with at least 8 ounces of water.
- Powder: The label provides about 2 g of methylcellulose per dose, measured as 1 heaping tablespoon for original Citrucel Orange or 1 rounded tablespoon for Citrucel Sugar Free, mixed into at least 8 ounces of water or juice, up to 3 times a day.
- Start with the lowest labeled dose and increase only as needed. Starting too high, too fast, is the most common reason people give up on any fiber supplement.
- The label advises you to stop use and ask a doctor if constipation lasts more than 7 days, or if you have rectal bleeding.
Citrucel comes in a few common formats:
- Citrucel Fiber Therapy Caplets (180 count), for people who would rather swallow a caplet than mix a drink.
- Citrucel Sugar-Free Fiber Powder, Orange Flavor (16.9 oz), the sugar-free version, relevant for anyone managing blood sugar or simply avoiding added sugar.
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If you are older or have struggled with gas from highly fermentable fiber sources in the past, our guide to sugar-free fiber supplements for seniors goes into more detail on how methylcellulose’s low-fermentation profile compares with other fiber choices.
Citrucel Side Effects
Citrucel is generally well tolerated. Because methylcellulose is minimally fermented by colonic bacteria, it may be less likely to cause gas than more highly fermentable fibers such as inulin. That said, side effects are still possible.
The most commonly reported side effects are:[6,9,11]
- Gas (generally less common than with more fermentable fibers, but still possible)
- Stomach discomfort or cramping
- Excessive bowel activity
The most important warning on the actual product label concerns choking or blockage: taking methylcellulose without enough liquid can cause it to swell and potentially block the throat or esophagus. Do not take it if you have difficulty swallowing, and seek immediate medical attention if you experience chest pain, vomiting, or difficulty swallowing or breathing after taking it.[11]
Citrucel should not be used, or should only be used under a doctor’s supervision, in the following situations:[6,11]
- Difficulty swallowing or a narrowed esophagus, since the caplets can swell and worsen swallowing difficulty
- Known or suspected bowel obstruction
- Symptoms of a serious gastrointestinal problem, such as sudden abdominal pain, nausea or vomiting, rectal bleeding, or a sudden, unexplained change in bowel habits
- Known allergy to methylcellulose or to any inactive ingredient in the specific product
- Phenylketonuria (PKU), for products that contain aspartame, such as the sugar-free powder, since these contain phenylalanine
A few additional safety points that are easy to miss on the label:
- Timing with other medications: Methylcellulose may affect the absorption of some oral medications when taken at the same time. Check the product label and ask your pharmacist or doctor whether you should separate Citrucel from your other medicines, especially if you take a medication with a narrow safety margin.[8]
- Pregnancy and breastfeeding: Check with a doctor before using Citrucel if you are pregnant or breastfeeding, as with most OTC medications.[6]
- When to call a doctor: The product label advises asking a doctor before use if you have abdominal pain, nausea, or vomiting, or a sudden change in bowel habits that persists for two weeks. Stop use and call a doctor if constipation lasts more than 7 days while using it.[11]
- Not habit-forming: Bulk-forming fibers like methylcellulose are not stimulant laxatives and are not generally associated with the type of laxative dependence sometimes discussed with long-term stimulant laxative misuse.
Citrucel vs Metamucil: Which Should You Choose?
Citrucel and Metamucil are both bulk-forming fiber laxatives, but they use different types of fiber, and that difference drives most of the practical distinctions between them.
| Factor | Citrucel (methylcellulose) | Metamucil (psyllium husk) |
|---|---|---|
| Fiber type | Semi-synthetic, low-fermentation soluble fiber | Natural, gel-forming soluble fiber (with some insoluble content) |
| Gas and bloating | Generally minimal, as a low-fermentation fiber | Can cause gas or bloating in some people, particularly if the dose is increased quickly, though many people tolerate it well |
| Depth of research | Effective in older clinical studies, but fewer modern trials specific to methylcellulose | Larger and more recent constipation evidence base among fiber types |
| Taste and texture | Dissolves relatively clear; caplets available for those who dislike drinks | Typically forms a thicker gel; caplets less common |
| Additional benefit | Primarily constipation and regularity | Also has an FDA-authorized health claim related to coronary heart disease risk reduction, when specific conditions are met |
Some of this comes down to fiber chemistry: methylcellulose is 100% soluble fiber, while psyllium forms a more viscous gel and carries some insoluble fiber alongside its soluble fraction, which is part of why psyllium can feel thicker or grittier to some people.[7]
If your main issue with fiber supplements has been the texture of psyllium drinks, or you simply prefer a low-fermentation fiber, Citrucel is a reasonable option to try. If you want the fiber type with the largest and most recent body of clinical trial evidence, or you are also managing cholesterol, psyllium-based Metamucil has the stronger research case.
For a deeper side-by-side comparison, including dosing and who each option suits best, see our Benefiber vs Metamucil comparison, which also covers where methylcellulose fits in.
Neither Citrucel nor Metamucil works as fast as an osmotic laxative. If you need faster relief while you get a fiber routine established, our MiraLAX vs Metamucil guide explains how the two approaches differ and when combining them may be worth discussing with a doctor.
What Do Real Users Say? Citrucel Review Ratings
On Drugs.com, Citrucel carries an average user rating of 9.8 out of 10, with 100% of its four reviewers reporting a positive effect. In the same comparison tool, psyllium carries an average rating of 7.3 out of 10 from 97 reviewers, with 67% reporting a positive effect and 25% reporting a negative one.[10]
That sounds like a landslide for Citrucel, but it is worth reading with real caution: a rating built on four reviews can easily land near-perfect, while a rating built on nearly a hundred reviews reflects a much wider range of real-world experiences. Treat this as a useful directional signal that Citrucel has satisfied the small number of people who rated it, not as statistical proof that it outperforms psyllium in general use.
Is Citrucel Right for You?
Citrucel tends to be a good fit if:
- You have tried psyllium and found the texture or gel-like consistency hard to tolerate
- You want a low-fermentation fiber option, or highly fermentable fibers like inulin have caused you noticeable gas
- You want a caplet form rather than a mixed drink
- You have occasional constipation, or chronic constipation that has already been evaluated by a doctor and for which a fiber supplement is an appropriate part of the plan
It is probably not the right first step if:
- Your constipation is severe, sudden, or accompanied by red-flag symptoms like rectal bleeding or unintended weight loss, all of which need a medical evaluation first
- You have trouble swallowing or a history of bowel obstruction
- You want the fiber option with the deepest and most current clinical trial support, in which case psyllium currently has the stronger evidence base
For a broader view of where Citrucel and other fiber options fit alongside osmotic and stimulant laxatives, our Best OTC Laxatives for Constipation guide compares all the major categories side by side.
Frequently Asked Questions About Citrucel
Does Citrucel help constipation?
Yes. Methylcellulose, the active ingredient in Citrucel, is a bulk-forming fiber laxative that has been shown in clinical studies to increase stool frequency, stool water content, and fecal solids in people with constipation.[1] It is also listed by the American Academy of Family Physicians as one of the standard OTC bulk-forming fiber supplements used to relieve constipation, alongside psyllium and polycarbophil.[5] As with any fiber supplement, it works best combined with adequate water intake.
How does Citrucel work?
Citrucel’s methylcellulose absorbs and retains water in the intestinal contents, forming a soft, bulky mass that softens the stool and increases its bulk. The added bulk stretches the intestinal wall and helps stimulate the muscle contractions (peristalsis) that move stool through the colon.[6]
How long does it take Citrucel to work?
Citrucel generally produces a bowel movement within 12 to 72 hours, consistent with other bulk-forming fiber laxatives.[11] It is meant for gradual, ongoing use rather than fast, same-day relief.
What are the main Citrucel side effects?
The most commonly reported side effects are gas, stomach discomfort, cramping, and excessive bowel activity. The most important label warning concerns choking or esophageal blockage if taken without enough fluid. Seek immediate medical attention if you experience chest pain, vomiting, or difficulty breathing or swallowing after taking it.[6,9,11]
How do I take Citrucel correctly?
Follow your specific product’s label. As a general guide, caplets are typically taken 2 at a time with at least 8 ounces of water, up to 6 times a day (maximum 12 caplets daily), while the powder provides about 2 g of methylcellulose per dose (1 heaping tablespoon for original Citrucel Orange, or 1 rounded tablespoon for Citrucel Sugar Free), mixed into at least 8 ounces of liquid, up to 3 times a day. Start with the lowest labeled dose and increase only as needed.
Citrucel vs Metamucil: which is better?
Neither is universally better. Citrucel (methylcellulose) is a low-fermentation fiber, so it is often chosen by people who want to avoid gas from more fermentable fibers like inulin, or who have not tolerated them well. Psyllium has stronger clinical evidence for constipation, and psyllium soluble fiber is eligible for an FDA-authorized coronary-heart-disease health claim under specified conditions.[4] The right choice depends on your tolerance and goals.
Is Citrucel safe for chronic, long-term use?
The 2023 AGA/ACG guideline suggests fiber supplementation over no fiber for chronic idiopathic constipation, but the evidence was low certainty and the guideline’s supporting trial data were strongest for psyllium; no randomized controlled trials of methylcellulose were available for its analysis.[3] The current Citrucel label is intended for occasional constipation and advises stopping use and asking a doctor if constipation lasts more than 7 days.[11] If you need treatment every day for ongoing constipation, discuss a longer-term plan with a healthcare professional.
Can I take Citrucel with other medications?
Because methylcellulose may affect the absorption of some oral medications, check the product label and ask your pharmacist whether you should separate Citrucel from your medicines, especially if you take a medication with a narrow safety margin.[8]
References
- Hamilton JW, Wagner J, Burdick BB, Bass P. Clinical evaluation of methylcellulose as a bulk laxative. Dig Dis Sci. 1988;33(8):993-998. doi:10.1007/BF01535996
- Snape WJ. The effect of methylcellulose on symptoms of constipation. Clin Ther. 1989;11(5):572-579.
- Chang L, Chey WD, Imdad A, et al. American Gastroenterological Association-American College of Gastroenterology Clinical Practice Guideline: Pharmacological Management of Chronic Idiopathic Constipation. Am J Gastroenterol. 2023;118(6):936-954. doi:10.14309/ajg.0000000000002227
- van der Schoot A, Drysdale C, Whelan K, Dimidi E. The effect of fiber supplementation on chronic constipation in adults: an updated systematic review and meta-analysis of randomized controlled trials. Am J Clin Nutr. 2022;116(4):953-969. doi:10.1093/ajcn/nqac184
- American Academy of Family Physicians (familydoctor.org). Laxatives: OTC Products for Constipation. Available at: familydoctor.org
- WebMD. Citrucel (methylcellulose) drug details. Available at: webmd.com/drugs/2/drug-169101-6109/fiber-laxative/details
- Healthline. Citrucel Powder: Is It Good for Constipation? Available at: healthline.com/nutrition/citrucel-powder
- Pharmacy Times. Clinical Evidence for OTC Products for Constipation. Available at: pharmacytimes.com
- RxList. Methylcellulose (Citrucel) generic drug information. Available at: rxlist.com/methycellulose/generic-drug.htm
- Drugs.com. Citrucel vs Psyllium comparison (user ratings). Available at: drugs.com/compare/citrucel-vs-psyllium
- Citrucel Drug Facts Label (methylcellulose powder, for solution, and methylcellulose caplets), Haleon US Holdings LLC, reproducing the FDA OTC drug facts label. Available at: drugs.com/pro/citrucel.html and drugs.com/pro/citrucel-tablets.html
This article is for general education and is not a substitute for medical advice. If your constipation is persistent, severe, or accompanied by blood in the stool, unexplained weight loss, vomiting, or severe abdominal pain, talk to a healthcare professional before treating it with an OTC laxative.
