Gaviscon (alginates)

What alginic acid / sodium alginate (with potassium or sodium bicarbonate, or aluminium hydroxide/magnesium carbonate depending on market formulation) is and how it works

Gaviscon is an over-the-counter medicine for heartburn and acid reflux (gastro-oesophageal reflux). Alginate-based versions work by forming a floating gel 'raft' on top of the stomach contents that physically blocks acid from splashing back into the food pipe (oesophagus); other formulations work as a more traditional antacid that neutralises stomach acid. (2) (1)

Gaviscon is intended for short-term, as-needed relief of heartburn and indigestion. If your symptoms do not improve within about a week, or keep coming back, see a doctor or pharmacist rather than continuing to self-treat.

Mechanism of action: how alginic acid / sodium alginate (with potassium or sodium bicarbonate, or aluminium hydroxide/magnesium carbonate depending on market formulation) works

Alginate-based formulations react with stomach acid to form a low-density, near-neutral-pH gel 'raft' that floats above the gastric contents and is preferentially refluxed instead of acid, providing a physical and chemical barrier effect lasting up to about 4 hours. Aluminium/magnesium-based formulations act as classic antacids, neutralising gastric acid directly. (2) (1)

What alginic acid / sodium alginate (with potassium or sodium bicarbonate, or aluminium hydroxide/magnesium carbonate depending on market formulation) is used for

Before taking alginic acid / sodium alginate (with potassium or sodium bicarbonate, or aluminium hydroxide/magnesium carbonate depending on market formulation)

Do not take / not appropriate for

• Do not take Gaviscon if you have had an allergic reaction to it or to any of its ingredients. (all countries) (2)

Tell your clinician about

• Whether you are on a low-sodium or low-potassium diet, or have heart failure or kidney problems, since some Gaviscon formulations contain meaningful amounts of sodium and/or potassium.
• All other medicines you take, especially antibiotics (tetracyclines, fluoroquinolones), iron supplements, or thyroid hormone, since Gaviscon can reduce how well these are absorbed if taken too close together.
• Pregnancy or breastfeeding, so the most appropriate formulation and dose can be confirmed for you.
• Whether your symptoms have lasted more than a week, are severe, or are accompanied by warning signs such as unexplained weight loss, difficulty swallowing, or vomiting blood -- these need medical assessment rather than ongoing self-treatment.

How to take alginic acid / sodium alginate (with potassium or sodium bicarbonate, or aluminium hydroxide/magnesium carbonate depending on market formulation)

• Check the specific product's label for its exact active ingredients and dose, since Gaviscon formulations vary by country and by product line (e.g. 'Advance', 'Extra Strength', 'Dual Action').
• Leave a gap of about 2 hours between taking Gaviscon and taking other oral medicines, particularly antibiotics, iron tablets, or thyroid hormone, since Gaviscon can reduce their absorption if taken at the same time.
• Alginate 'Advance'-type formulations are usually taken after meals and at bedtime, since this is when reflux is most likely.

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6)

Missed dose

Gaviscon is usually taken as needed for symptoms rather than on a fixed schedule, so a 'missed dose' does not generally apply -- simply take the next dose when you next have symptoms, without exceeding the maximum daily amount on the label.

Overdose

Taking much more than the labelled maximum daily dose is unlikely to cause serious harm for most people, but can cause stomach upset, and in people with kidney problems or on a low-sodium/potassium diet could contribute to a higher intake of these minerals than intended. If a large amount has been swallowed, especially by a child, or if you feel unwell, contact a doctor, pharmacist, or poison control for advice. (2)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Serious warnings

Interactions

• Leave about a 2-hour gap between Gaviscon and other oral medicines, especially tetracycline or fluoroquinolone antibiotics, iron supplements, and thyroid hormone tablets, since taking them together can reduce how much of those medicines your body absorbs. (2)
• Aluminium/magnesium-containing formulations (such as the US product) can also reduce the absorption of some other medicines when taken at the same time -- the same 2-hour spacing principle applies generally to antacids. (1)

Pregnancy, breastfeeding, kidney/liver function, age

Monitoring

Before starting

• Confirm the symptoms are ordinary heartburn/reflux and not a warning sign needing medical assessment (see serious warnings).

During treatment

• Review with a doctor or pharmacist if symptoms have not improved within about 7 days.
• Do not use the maximum labelled dose for more than 2 weeks without medical supervision.
• Watch for new or worsening symptoms such as difficulty swallowing or weight loss, which need medical review.

Storage

Store at room temperature, away from heat and moisture, as directed on the product label. Keep out of reach of children.

Frequently asked questions

References

1. GAVISCON (aluminum hydroxide and magnesium carbonate) liquid antacid -- Drug Facts labelU.S. Food and Drug Administration / DailyMed (NIH), OTC Drug Facts label · United States · accessed 2026-07-29 · source 1
2. Gaviscon Advance Peppermint Flavour Oral Suspension -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom -- Reckitt Benckiser Healthcare (UK) Ltd · United Kingdom · accessed 2026-07-29 · source 2
3. Gaviscon Advance Chewable Tablets (sodium alginate 500 mg, potassium hydrogen carbonate 100 mg) -- Summary of Product Characteristics / LicenceHealth Products Regulatory Authority (HPRA), Ireland -- an EU member state competent authority · European Union · accessed 2026-07-29 · source 3
4. GAVISCON LIQUID - Fruit & Mint Flavours (DIN 02142643) -- historical DPD listing; current Gaviscon Regular/Extra Strength products remain marketed in Canada under the Gaviscon brand (Haleon/GSK Consumer Healthcare)Health Canada Drug Product Database (DPD) · Canada · accessed 2026-07-29 · source 4
5. GAVISCON DUAL ACTION mixed berry flavour oral liquid -- ARTG entryTherapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-29 · source 5
6. Gaviscon Original / Dual Action / Extra Strength -- New Zealand retail availabilityNew Zealand general-sale medicine market confirmation (Chemist Warehouse NZ, Unichem NZ pharmacy retail listings) · New Zealand · accessed 2026-07-29 · source 6

Brand names by country

Single-ingredient alginic acid / sodium alginate (with potassium or sodium bicarbonate, or aluminium hydroxide/magnesium carbonate depending on market formulation) names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries