Gaviscon contains a combination of antacid and alginate ingredients designed to neutralize stomach acid and physically block it from rising into the esophagus. The exact ingredients depend on which version you buy, and formulations differ significantly between the US and UK markets. Here’s what’s in each version and how the ingredients work together.
Active Ingredients by Formulation
Gaviscon isn’t a single product. It comes in several versions, and the active ingredients vary quite a bit depending on which one you pick up.
The US Regular Strength liquid contains aluminum hydroxide and magnesium carbonate as its active antacid ingredients. Each tablespoon (15 mL) delivers about 115 mg of magnesium and 52 mg of sodium. The US Extra Strength version uses the same two active ingredients in a more concentrated form, with each teaspoon (5 mL) containing roughly 75 mg of magnesium and 11 mg of sodium.
UK and European versions take a different approach. Gaviscon Double Action Liquid, widely sold outside the US, contains 1,000 mg of sodium alginate, 426 mg of sodium bicarbonate, and 650 mg of calcium carbonate per 20 mL dose. The alginate is the star ingredient here, and it plays a role the traditional antacid ingredients don’t.
How Sodium Alginate Works
Sodium alginate is a natural polymer extracted from brown seaweed. When it hits stomach acid, it transforms within a few minutes into a thick, gel-like layer that floats on top of your stomach contents. The sodium bicarbonate in the formula reacts with acid to release carbon dioxide gas, which gets trapped inside the gel and gives it buoyancy, like tiny air pockets in a life raft. This floating barrier sits right at the junction between your stomach and esophagus, physically preventing acid from splashing upward.
This “raft” mechanism is distinct from how traditional antacids work. Aluminum hydroxide and magnesium carbonate simply neutralize acid chemically. The alginate raft does something more targeted: it eliminates what researchers call the “acid pocket,” a pool of highly acidic fluid that forms on top of your meal and is the primary source of post-meal reflux. In clinical studies, the alginate-based formulation was more effective at controlling acid exposure in the esophagus than antacids alone.
How Long the Ingredients Stay Active
Timing matters with Gaviscon. When taken 30 minutes after a meal, the raft stays in the stomach for roughly 3 hours on average before the stomach empties it. If you take it on an empty stomach, though, it clears in about 20 minutes and provides almost no benefit. Taking it before a meal doesn’t work either, because the raft can’t float on food that arrives after it. For best results, take it shortly after eating.
Inactive Ingredients
Beyond the active compounds, Gaviscon liquids contain a range of inactive ingredients that affect texture, taste, shelf life, and appearance. In the US Regular Strength liquid, these include benzyl alcohol (a preservative), saccharin sodium (an artificial sweetener), glycerin, sorbitol solution, sodium alginate (used here as a thickening agent rather than an active ingredient), xanthan gum, edetate disodium, and food coloring (D&C Yellow #10 and FD&C Blue #1).
The US Extra Strength versions in Cool Mint and Cherry flavors swap the food dyes for natural and artificial flavors and add simethicone emulsion, which helps reduce gas and foaming.
UK formulations list different excipients. Gaviscon Peppermint Liquid Relief contains carbomer (a thickening polymer), methyl parahydroxybenzoate (E218) and propyl parahydroxybenzoate (E216) as preservatives, saccharin sodium, peppermint oil, sodium hydroxide, and water. The parahydroxybenzoate preservatives (parabens) can cause allergic reactions in some people, sometimes with a delayed onset.
Sodium Content for Restricted Diets
If you’re watching your salt intake, the sodium levels in Gaviscon are worth knowing. The US Regular Strength liquid contains 52 mg of sodium per tablespoon. The US Extra Strength contains just 11 mg per teaspoon. The UK Double Action formulation is higher: each 20 mL dose includes 426 mg of sodium bicarbonate as an active ingredient, contributing a more significant sodium load. If you’re on a sodium-restricted diet, the US Extra Strength version delivers the least sodium per dose.
Interactions With Other Medications
Several Gaviscon ingredients can interfere with how your body absorbs other medications. The calcium, magnesium, and aluminum in various formulations carry a positive charge that binds to certain drugs in your digestive tract, forming insoluble clumps your body can’t absorb. Antibiotics in the tetracycline family are particularly affected by this. Iron supplements and some thyroid medications run into the same problem.
The fix is straightforward: separate your doses. Taking Gaviscon at least two hours before or after other medications generally prevents these interactions from reducing the effectiveness of your other prescriptions.