Yes, Gaviscon is an alginate-based product. Its primary active ingredient is sodium alginate, a natural compound derived from seaweed that works differently from traditional antacids. While Gaviscon also contains antacid ingredients like calcium carbonate or magnesium carbonate depending on the formulation, the alginate is what sets it apart and drives its main mechanism of action.
How the Alginate in Gaviscon Works
Sodium alginate does something no ordinary antacid can: it forms a physical barrier on top of your stomach contents. When the alginate meets stomach acid, it reacts with bicarbonate in the formula to create a foamy, gel-like “raft” that floats on the surface of whatever is in your stomach. This raft sits between your stomach contents and the opening to your esophagus, acting like a lid.
During a reflux episode, the raft can move into the esophagus ahead of acidic stomach contents, essentially shielding the sensitive tissue there. In some cases, it physically prevents stomach contents from traveling upward at all. This is a mechanical approach to reflux rather than a purely chemical one. Traditional antacids neutralize acid that’s already there, but they don’t stop it from splashing back up. The alginate raft addresses the splash itself.
What’s Actually in Each Dose
Gaviscon comes in several formulations, and the alginate content varies between them. Gaviscon Advance, one of the more widely used versions, contains 1,000 mg of sodium alginate per 10 ml dose along with 200 mg of potassium bicarbonate. It also includes 200 mg of calcium carbonate. The bicarbonate reacts with stomach acid to generate carbon dioxide bubbles, which get trapped in the alginate gel and help the raft float.
The U.S. formulations differ from the UK versions. American Gaviscon Regular Strength relies more heavily on aluminum hydroxide and magnesium carbonate as its listed active antacid ingredients, with alginic acid included as well. So while all Gaviscon products use alginate technology, the exact balance of alginate to antacid ingredients depends on which version you’re using and where you bought it.
Alginate vs. Traditional Antacids
Standard antacids like calcium carbonate (Tums) or magnesium hydroxide (Milk of Magnesia) work by chemically neutralizing stomach acid. They’re effective, but the relief tends to be shorter-lived because they don’t prevent new acid from causing problems. Alginate-based products combine both approaches: the antacid component neutralizes existing acid while the alginate raft provides a longer-lasting physical barrier.
Research comparing the two shows alginate-based antacids offer a faster onset of relief paired with a longer duration of symptom control. Studies measuring how long different products neutralize gastric acid found significant variation, with durations ranging from 21 to 88 minutes depending on raft quality. The best-performing alginate rafts had an optimum porosity that allowed them to absorb and neutralize acid over a sustained period. This makes alginate formulations particularly useful for postprandial heartburn, the kind that flares up after meals.
When and How to Take It
Timing matters with alginate products because the raft needs something to float on. The NHS recommends taking Gaviscon after meals and at bedtime, since reflux symptoms are typically worst during those windows. Taking it on a completely empty stomach is less effective because there’s no gastric pool for the raft to sit on top of.
For nighttime reflux, a dose at bedtime helps the raft form before you lie down, which is when gravity stops helping keep stomach contents in place.
Sodium Content and Medication Interactions
Because Gaviscon contains sodium alginate and sodium bicarbonate, each dose adds some sodium to your intake. The U.S. Regular Strength formula contains about 52 mg of sodium per tablespoon, while the Extra Strength version has around 11 mg per teaspoon. If you’re watching your sodium intake for blood pressure or heart health, these amounts are worth factoring in, especially with repeated daily dosing.
Alginate can also interfere with how your body absorbs certain medications. Thyroid hormone replacement is one notable example. Sodium alginate has been identified among the substances that can impair absorption of thyroid medication. If you take any daily prescriptions, spacing them apart from your Gaviscon dose (typically by at least two hours) helps avoid this issue.
Safety During Pregnancy
Heartburn is extremely common during pregnancy, and Gaviscon is one of the go-to options. The NHS confirms it can be taken during pregnancy, provided you follow the recommended dosing. Its mechanical mode of action, forming a physical barrier rather than being absorbed systemically, is part of why it’s considered a lower-risk choice. If symptoms persist despite using it, a pharmacist or doctor can suggest alternatives, but Gaviscon is generally the first-line recommendation for pregnancy-related reflux.