Gaviscon starts working within minutes of swallowing it, and most people feel relief in under 30 minutes. Unlike acid-reducing medications that need time to absorb into the bloodstream, Gaviscon works physically inside the stomach, which is why the effect is almost immediate.
How Gaviscon Works So Quickly
Gaviscon doesn’t reduce acid production the way most heartburn medications do. Instead, it contains sodium alginate, a seaweed-derived compound that reacts with stomach acid to form a thick, gel-like layer that floats on top of your stomach contents. Carbon dioxide gets trapped inside this gel, keeping it buoyant. The result is a physical barrier, sometimes called a “raft,” that sits between the acidic contents of your stomach and your esophagus. When you burp or bend over, this raft blocks acid from splashing upward.
Because this process is a chemical reaction rather than something your body needs to digest and absorb, it begins as soon as the liquid or tablet meets stomach acid. Gaviscon also contains antacid ingredients like calcium carbonate that neutralize some acid on contact, giving you a second layer of relief in those first few minutes.
Gaviscon vs. Other Heartburn Medications
A clinical study comparing sodium alginate (Gaviscon’s active ingredient) to two common prescription heartburn drugs found that alginate was significantly better at preventing acid from reaching the esophagus during the first hour after dosing. Nearly half of patients on alginate-based therapy (49.4%) experienced rapid relief within 30 minutes, compared to about 40% of those taking a standard antacid.
Proton pump inhibitors (PPIs) like omeprazole work by shutting down acid-producing pumps in the stomach lining, but they need to be absorbed into the bloodstream first. That means they can take one to three days of regular use to reach full effect. H2 blockers like ranitidine start showing a meaningful advantage only after about two hours. Gaviscon fills the gap when you need something that works right now.
That said, Gaviscon isn’t designed for long-term acid suppression. PPIs and H2 blockers are better suited for chronic conditions like GERD because they reduce overall acid production throughout the day. Gaviscon is best for on-demand, fast-acting relief.
How Long the Relief Lasts
A single dose of Gaviscon typically provides relief for two to four hours, depending on how much food is in your stomach and how active you are. The alginate raft stays intact as long as stomach contents remain relatively still. Once the stomach empties, the raft breaks down and passes through the digestive system harmlessly.
This is why you can take Gaviscon up to four times a day: after each meal and at bedtime. Taking it after eating is ideal because a full stomach gives the raft a stable surface to float on, and post-meal periods are when reflux is most likely to occur. If you take it on an empty stomach, the raft forms but may not last as long because there’s less content to anchor it.
Getting the Best Results
Timing matters more than most people realize. Taking Gaviscon right after a meal, rather than waiting until symptoms start, lets the raft form before acid has a chance to splash into the esophagus. Bedtime doses are especially useful if you experience nighttime heartburn, since lying down makes reflux worse.
If you’re using the liquid form, shake the bottle well. The alginate and antacid components can settle, and an uneven dose means a weaker raft. Chewable tablets should be chewed thoroughly before swallowing, since the reaction depends on the ingredients mixing with stomach acid evenly.
Avoid taking Gaviscon at the same time as other medications. The antacid components can interfere with how your body absorbs certain drugs. Spacing them at least two hours apart is a practical rule of thumb.
Who Should Be Cautious
Gaviscon is available over the counter and is generally well tolerated, but it does contain sodium and magnesium. A tablespoon of regular-strength Gaviscon liquid contains about 52 mg of sodium. That’s a small amount compared to dietary sodium, but if you’re on a sodium-restricted diet for blood pressure or heart-related reasons, it adds up over multiple daily doses. The extra-strength version contains significantly less sodium per dose, around 11 mg.
People with kidney disease should check with a pharmacist before using Gaviscon, since the kidneys handle the magnesium it contains. The same applies if you’re on a magnesium-restricted diet or taking prescription medications that could interact with antacids.