What Is in Gaviscon? Active and Inactive Ingredients

Gaviscon’s active ingredients depend on which version you pick up and where in the world you buy it, but the signature component across most formulations is sodium alginate, a seaweed-derived compound that forms a floating gel barrier on top of stomach contents. Other active ingredients vary by product and region: some versions lean heavily on traditional antacids like aluminum hydroxide or calcium carbonate, while others pair the alginate with sodium bicarbonate or potassium bicarbonate. The differences are not just branding. They change how the product works inside your body and which reflux problems it handles best.

The Core Active Ingredients

Gaviscon products sold in the UK, much of Europe, and many other international markets center on sodium alginate as the primary active ingredient. Alginate is a natural polysaccharide extracted from brown seaweed. When it hits gastric acid, it precipitates into a gel. Formulations typically include sodium bicarbonate or potassium bicarbonate as a second active ingredient; the bicarbonate reacts with stomach acid to produce carbon dioxide gas, which gets trapped inside the gel and turns it into a buoyant foam that floats on top of stomach contents like a raft.¹ A third active ingredient, calcium carbonate, appears in several versions and serves dual duty: it acts as a conventional antacid that neutralizes acid on contact, and the calcium ions also cross-link with the alginate to strengthen the raft structure.

The US formulation of Gaviscon is a genuinely different product. It lists aluminum hydroxide and magnesium carbonate as the primary active ingredients, making it closer to a traditional antacid than to the alginate-forward versions sold elsewhere. Some US versions do contain alginate, but it is listed as an inactive ingredient rather than the star of the formula. This matters because the physical raft mechanism, which is the main selling point of Gaviscon in the UK, plays a smaller role in the American version.

How the Formulations Differ by Product Line

Even within a single country, the Gaviscon family includes multiple products with meaningfully different ingredient lists. In the UK and international markets, three main variants dominate the shelf:

Gaviscon Original: Contains sodium alginate, sodium bicarbonate, and calcium carbonate. This is the classic formula that combines raft formation with moderate antacid activity.
Gaviscon Advance: Contains a higher concentration of sodium alginate paired with potassium bicarbonate. The increased alginate load builds a stronger, longer-lasting raft. This version contains no traditional antacid salts like calcium carbonate, so it relies almost entirely on the physical barrier rather than acid neutralization.
Gaviscon Double Action: Combines sodium alginate with both calcium carbonate and sodium bicarbonate, giving it both the raft mechanism and more robust acid-neutralizing power.

Gaviscon Infant, designed for babies with regurgitation, uses a combination of sodium alginate and magnesium alginate. It is formulated as a powder that gets mixed into feeds. This version is deliberately aluminum-free, which was a specific design goal given concerns about aluminum exposure in infants.²

The Inactive Ingredients

Beyond the active ingredients, Gaviscon products contain a range of inactive ingredients that keep the liquid stable, palatable, and properly textured. The exact list varies by product and flavor, but common inactive ingredients across the liquid formulations include:

Carbomer: A thickening agent that gives the liquid its viscous, gel-like consistency.
Methyl and propyl parahydroxybenzoates: Preservatives (sometimes listed as methylparaben and propylparaben) that prevent microbial growth in the liquid.
Sodium saccharin or sucralose: Sweeteners that mask the chalky, salty taste of the active salts.
Flavoring agents: Peppermint or anise flavors are common, depending on the version.
Purified water: The base of the liquid suspension.

Tablet versions of Gaviscon swap out the liquid-specific stabilizers for dry binding agents, compression aids, and coating materials. If you are avoiding specific additives for allergy or dietary reasons, the inactive ingredient lists between the liquid and the chewable tablet are quite different and worth reading separately.

What the Raft Actually Does Inside Your Stomach

The mechanism that sets alginate-based Gaviscon apart from a standard antacid is physical, not purely chemical. When you swallow the liquid, the sodium alginate meets hydrochloric acid in your stomach and rapidly gels. Simultaneously, the bicarbonate reacts with that acid to produce carbon dioxide bubbles, which inflate the gel into a floating foam. The result is a spongy barrier sitting on top of whatever you just ate.

This raft does something a standard antacid cannot: it physically blocks stomach contents from splashing up into your esophagus. After a meal, a pool of newly secreted unbuffered acid tends to sit on top of the food in your stomach, right at the junction where the esophagus meets the stomach. Researchers call this the “acid pocket,” and it is a major driver of postprandial reflux. Studies using pH sensors positioned along the esophagus and stomach have shown that the alginate raft can eliminate or displace this acid pocket, pushing it away from the vulnerable junction.³ A separate study confirmed that the raft localizes directly to where the acid pocket forms and displaces it below the diaphragm.⁴

The strength of that raft depends on several interacting factors: how much carbon dioxide gets trapped, the molecular properties of the particular alginate used, and whether calcium or aluminum ions are present to cross-link the gel.⁵ In lab testing, formulations that produced stronger, more cohesive rafts also resisted simulated reflux events better. This is partly why Gaviscon Advance, with its higher alginate concentration, tends to perform differently than Gaviscon Original in clinical comparisons.

How Gaviscon Compares to Plain Antacids

A calcium carbonate tablet or a magnesium hydroxide suspension works by chemically neutralizing stomach acid. The effect is fast but relatively brief, and once the acid is neutralized, there is no ongoing physical barrier. Gaviscon’s alginate raft, by contrast, can persist in the stomach for several hours, continuing to block reflux mechanically even after the initial acid-neutralizing effect fades.

In a double-blind crossover trial comparing Gaviscon Double Action to a matched antacid without alginate, patients who took the alginate-antacid combination had significantly less acid exposure in the lower esophagus during the 30-to-150-minute window after a meal. The number of reflux events was similar between the two treatments, but the acid content reaching the esophagus was lower with Gaviscon, suggesting the raft was diluting or buffering what did splash up.⁶

A similar pattern showed up in a trial comparing Gaviscon Advance to a non-alginate antacid taken after late-night meals. The alginate formulation suppressed the acid pocket more effectively and reduced the percentage of time the esophagus spent at a low pH, while the standard antacid did not achieve the same results.⁷ The practical takeaway is that if your reflux is mainly triggered by meals and positional changes, the physical barrier may matter more to you than raw acid-neutralizing power.

Using Gaviscon Alongside Proton Pump Inhibitors

Many people with persistent reflux are already taking a proton pump inhibitor (PPI) like omeprazole or lansoprazole and still get breakthrough symptoms. The question of whether adding Gaviscon helps on top of a PPI has been tested directly. In one trial, adding Gaviscon Advance to once-daily PPI therapy produced a significantly greater reduction in reflux symptoms compared to placebo, with a meaningful drop in the number of nights patients experienced symptoms.⁸

A two-phase study of Gaviscon Double Action as add-on therapy told a more complicated story. The initial exploratory phase found that patients taking the alginate-antacid had significantly better heartburn and regurgitation scores than those on placebo, with three-quarters of Gaviscon patients achieving clinically meaningful improvement compared to just over a third on placebo. But the larger confirmatory phase of the same study did not find a statistically significant difference, with roughly half of patients in both groups improving.⁹ The placebo response in reflux trials tends to be high, which makes it genuinely difficult to demonstrate add-on benefit in large studies even when patients report feeling better. If you are already on a PPI and still getting symptoms, adding an alginate product at bedtime or after meals is a reasonable and low-risk strategy, but the evidence that it will consistently outperform a dummy dose is less airtight than the evidence for its standalone use.

Gaviscon for Throat and Airway Reflux

Reflux does not always stop at the esophagus. When stomach contents reach the throat and voice box, it causes laryngopharyngeal reflux (LPR), which can produce a chronic cough, hoarseness, throat clearing, and a feeling of a lump in the throat. The tissue lining the throat is far more sensitive to acid and pepsin than the esophageal lining, so even small amounts of reflux can cause disproportionate irritation.

Gaviscon Advance has shown particular promise here. A study comparing Gaviscon Advance alone to Gaviscon Advance combined with a high-dose PPI found that the alginate product by itself was effective in treating LPR symptoms, and adding a PPI did not provide additional benefit.¹⁰ This is a striking finding because PPIs are the default prescription for reflux-related throat problems, yet alginates may address LPR through a different and arguably more relevant mechanism: by physically preventing stomach contents from reaching the throat in the first place, and by coating the throat tissue during swallowing.

Lab research has shown that alginate formulations can preserve the epithelial barrier of aerodigestive tissue during exposure to pepsin and acid, suggesting the protection is partly topical, not just about blocking reflux events at the stomach.¹¹ If you have throat symptoms that your doctor suspects are reflux-related but PPIs have not resolved, an alginate-based Gaviscon may be worth discussing.

Safety During Pregnancy

Heartburn affects a large proportion of pregnant women, especially in the third trimester, and treatment options are limited because many medications carry uncertain fetal safety profiles. Alginate-based Gaviscon has been studied specifically in this population. A large prospective study of Liquid Gaviscon in pregnant women found that treatment was deemed successful in about 90% of patients, with very few adverse events related to the medication. Serum sodium levels, a potential concern with sodium-containing products, remained unchanged.¹²

A separate study of Gaviscon Advance during pregnancy reported similarly high efficacy ratings, with the majority of women reporting symptom relief within ten minutes of a dose.¹³ The fact that alginates work primarily through a physical mechanism rather than systemic absorption is part of what makes them attractive during pregnancy. The alginate raft stays in the stomach and is eventually broken down and excreted; very little enters the bloodstream.

The Infant Formulation

Gaviscon Infant uses sodium alginate and magnesium alginate as its active ingredients, deliberately omitting the aluminum salts found in some older pediatric preparations. In a placebo-controlled trial, this aluminum-free alginate formulation was more effective than placebo at reducing regurgitation episodes in infants.² A study using pH monitoring in 40 infants found that at least three reflux-related measurements improved by more than 10% in about three-quarters of the babies during the alginate period, with no significant difference between magnesium alginate and sodium alginate in how well they performed.¹⁴

One practical consideration with Gaviscon Infant is how it interacts with different milk formulas. An in vitro study simulating the infant stomach found that Gaviscon Infant reduced the height of refluxate across various milk types, including extensively hydrolyzed, partially hydrolyzed, and amino acid-based formulas. Performance varied by specific product, but at least one formula from each category outperformed the benchmark of standard unhydrolyzed formula.¹⁵ Parents using specialized formulas for cow’s milk protein allergy should know that Gaviscon Infant is still expected to form a functional raft, though the strength may vary depending on the specific formula.

Sodium Content and Other Practical Concerns

Because many Gaviscon formulations contain sodium alginate and sodium bicarbonate, the sodium content per dose is worth checking if you are on a low-sodium diet for blood pressure or heart failure management. A single dose of Gaviscon Original liquid can contain several hundred milligrams of sodium. Gaviscon Advance substitutes potassium bicarbonate for sodium bicarbonate, which reduces the sodium load somewhat, but sodium alginate itself still contributes. If you are monitoring sodium intake closely, the tablet forms generally contain less sodium per dose than the liquids, and it is worth comparing the labels.

Aluminum content is another practical concern, mainly in older formulations and the US version. Aluminum hydroxide is the primary active ingredient in US Gaviscon, and while the amounts are not considered dangerous for healthy adults at recommended doses, people with impaired kidney function should be cautious because they clear aluminum less efficiently. The UK and international formulations have largely moved away from aluminum in their ingredient lists, and the infant formulation was specifically redesigned to be aluminum-free.

Calcium carbonate, present in Gaviscon Original and Double Action, has its own ceiling. Excessive intake can lead to milk-alkali syndrome, a condition where high calcium combined with an alkaline agent raises blood calcium to problematic levels. At standard Gaviscon doses this is not a realistic concern, but it becomes relevant if you are also taking calcium supplements, eating calcium-fortified foods aggressively, or chewing calcium-based antacid tablets on top of Gaviscon. Stacking calcium from multiple sources is the scenario to watch out for, not Gaviscon by itself.

Why the US and UK Products Are So Different

The divergence between American and international Gaviscon is a historical quirk of licensing. The brand was originally developed in the UK in the 1960s as an alginate-based reflux suppressant. When it was licensed for the US market, the formulation was adapted to emphasize aluminum hydroxide and magnesium carbonate, ingredients that fit neatly into the existing US regulatory category of antacids. Over the decades, the UK product line continued evolving around the alginate mechanism, producing Gaviscon Advance and Double Action, while the US version stayed closer to a conventional antacid with alginate as a secondary player.

This creates genuine confusion for people who read about Gaviscon’s raft-forming action in research papers or UK-based health advice and then buy the American product expecting the same thing. Most of the clinical trials described in this article used the UK or international formulations, particularly Gaviscon Advance and Double Action. If you are in the US and want the alginate-forward version, some people import Gaviscon Advance from the UK through online retailers, though this is buying an unregulated import rather than an FDA-reviewed product. It is worth understanding that “Gaviscon” on the US shelf and “Gaviscon” in a European pharmacy are functionally different medications sharing a name.