Medicines for indigestion, heartburn and reflux fall into a few groups that work differently and carry different considerations.
- Antacids neutralise acid that is already there. They work within minutes and wear off quickly. See antacid side effects.
- Alginates form a raft on top of the stomach contents to reduce reflux. See Gaviscon side effects.
- Acid-reducing medicines lower how much acid the stomach makes. They take longer to work and last much longer, and are the group where long-term use raises questions.
Common side effects of this pharmacy medicine or category
- Antacids: constipation from aluminium-containing products, diarrhoea from magnesium-containing ones. Many combine both to balance this out.
- Alginates: generally well tolerated; bloating or wind occasionally.
- Acid-reducing medicines: headache, diarrhoea or constipation, nausea, abdominal pain and wind.
Long-term acid suppression has recognised considerations, which is why these are not intended to be taken indefinitely without review: reduced absorption of vitamin B12, magnesium and iron; a possible effect on bone density over years; and a somewhat higher risk of certain gut infections, since stomach acid is part of the body’s defence.
None of that means they should be avoided when needed. It means long-term use deserves a periodic conversation about whether the lowest effective dose is being used.
Interactions and duplicate-ingredient risks
Antacids block the absorption of several medicines taken at the same time, including thyroid medicine, some antibiotics, and iron. Separate them by a couple of hours. See levothyroxine side effects.
A point worth knowing about stopping acid-reducing medicines: stopping abruptly after a long course can cause rebound symptoms as acid production temporarily overshoots. That can feel like proof you still need them, when it may be a temporary effect of stopping. Reducing gradually usually avoids it, so ask rather than simply stopping and restarting.
Also worth checking: indigestion is often caused by another medicine, particularly anti-inflammatories. Treating the symptom while continuing the cause is a partial fix. See NSAID side effects.
Children, pregnancy, older adults and chronic medicine cautions
- Pregnancy. Heartburn is common, and several options are suitable, but check which.
- Kidney disease or heart failure. Some antacids contain significant sodium or affect electrolytes.
- Older adults on several medicines, where absorption interactions matter more.
Warning signs and overdose concerns
See a doctor rather than self-treating for:
- Difficulty or pain on swallowing, or food sticking
- Unexplained weight loss
- Vomiting blood, or black tarry stools
- Persistent vomiting
- Indigestion that is new and persistent, particularly over the age of 55
- Symptoms that keep returning as soon as you stop treatment
Chest pain is not always indigestion. Pain with breathlessness, sweating, or pain spreading to the arm or jaw needs emergency assessment rather than an antacid.
Questions to ask a pharmacist before using it
- Which type suits my symptoms?
- Could one of my medicines be causing this?
- Does it need separating from my other tablets?
- How long can I use it before seeing a doctor?
- I have been on an acid-reducing medicine for years. Should that be reviewed?
Related OTC and medicine-safety guides
- OTC medicine side effects
- Digestive medicine side effects
- Over-the-counter medicine interactions
- When to see a doctor about an OTC medicine
- Report an OTC medicine side effect
See also heartburn medicine side effects and Eno.
Medical Disclaimer: This content is for informational and educational purposes only and does not constitute medical diagnosis, prescription, or professional advice. Always read the patient information leaflet and consult a qualified doctor or pharmacist regarding any medicine or health concern.