Gaviscon: what it treats, how to take it, side effects
Last updated September 3, 2026.
Gaviscon is an over-the-counter antacid with a mechanical twist: its alginate forms a foam raft that floats on top of stomach contents, physically blocking acid from splashing up into the esophagus. That makes it the antacid aimed specifically at reflux and heartburn after meals, not just generic stomach acid.
What does it treat?
Heartburn, acid indigestion, sour stomach, and the upset stomach that comes with them, especially the post-meal and lying-down-at-night pattern where reflux does its worst. The raft-forming alginate plus the antacid (aluminum hydroxide and magnesium carbonate in the extra-strength tablets) neutralizes acid and then sits on top of it.
How do you take it?
The extra-strength tablets: chew 2 to 4 tablets four times a day, after meals and at bedtime, or as needed, and the label is specific that they must be chewed, not swallowed whole, followed by half a glass of water for best results. Liquid versions are taken by the spoonful on the same after-meals schedule. It is for adults and children 12 and older at those doses; younger kids need a doctor. If you need it daily for more than 2 weeks, that is a see-the-doctor line, not a lifestyle.
Side effects to know
- Common: essentially none for most people; the NHS calls it a very safe medicine, and what does occur (mild nausea, constipation from the aluminum, loose stools from the magnesium) is mild and stops when you stop.
- Serious: rare allergic reactions. The realistic cautions are the salt and mineral content: each extra-strength tablet carries sodium and magnesium, which matters on sodium-restricted diets and in kidney disease.
Who should not take it?
Check with a doctor or pharmacist first if you are on a sodium-restricted diet, have kidney disease, or take prescription drugs, because antacids interfere with absorption of several of them (antibiotics like tetracyclines and fluoroquinolones, iron, thyroid medicine): separate by 2 to 4 hours. It is a pregnancy-compatible option per the NHS, but at labeled doses, and daily-weeks-long use in anyone deserves a look at why.
When is it an emergency?
Heartburn red flags never change: chest pain (never assume it is reflux), vomiting blood, black tarry stools, trouble swallowing, or unintended weight loss all get emergency evaluation, not more antacid. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
What a Pymander AI doctor consult looks like
Illustrative example, not a real member's messages.
Common questions
How is Gaviscon different from Tums or regular antacids?
Plain antacids (Tums, Rolaids) just neutralize acid chemically. Gaviscon adds alginate, which reacts with stomach acid to form a foam raft floating on the stomach contents, physically blocking reflux when you bend over or lie down. For acid indigestion alone they are comparable; for reflux, the raft is the edge.
When should I take it for best effect?
After meals and at bedtime, per the label. That timing puts the raft in place exactly when reflux risk peaks: a full stomach, and lying down. Taking it on an empty stomach mid-morning wastes the mechanism.
Do I have to chew the tablets?
Yes. The label says do not swallow whole: chewing breaks the tablet down so the alginate can hydrate and form the raft, and following with half a glass of water helps it along. Whole-swallowed tablets largely fail at their own job.
Can I take it every day?
Short stretches, fine; daily for more than 2 weeks is the labeled see-a-doctor threshold. Persistent heartburn that needs daily suppression deserves a diagnosis (and possibly an H2 blocker like famotidine or a PPI), because masking it with antacids delays finding ulcers, Barrett's, or worse.
Is Gaviscon safe in pregnancy?
It is the UK NHS's standard suggestion for pregnancy heartburn, since the raft works mechanically and systemic absorption is minimal. Normal doses are considered compatible; the routine advice is still to run any regular medication past your own clinician, and lifestyle measures (smaller meals, not lying down after eating) come first.
Does it interact with my other medicines?
Antacids generally bind or pH-block other drugs: tetracycline and fluoroquinolone antibiotics, iron supplements, levothyroxine, and some antifungals all lose absorption. The standard fix is separating them by 2 to 4 hours. If you take daily prescriptions, a five-minute pharmacist check is worth it.