Antacids are a type of medication that can control the acid levels in your stomach.
They're available over the counter from pharmacies and are often used to treat the symptoms of heartburn and indigestion.
How antacids work
Antacids counteract (neutralise) the acid in your stomach that's used to aid digestion. This helps reduce the symptoms of heartburn and relieves pain.
Some antacids also coat the surface of the oesophagus (gullet) with a protective barrier against stomach acid, or produce a gel on the stomach’s surface which helps stop acid leaking into the oesophagus and causing acid reflux.
Different types of antacids
Antacids are available in liquid form or as chewable tablets. They're sold under various brand names but contain common ingredients, including:
Extra ingredients are sometimes added to help treat other problems, such as simeticone to relieve flatulence (wind), and alginates to prevent acid flowing into your oesophagus.
Who can't take antacids?
Antacids aren't suitable for everyone. For example, many antacids aren't recommended for children under the age of 12 and people with certain health conditions, such as kidney disease.
Antacids can also interfere with other medications, so you may not be able to take them while you're being treated for another condition.
Antacids are generally considered safe to take during pregnancy, but you should discuss it with your GP or pharmacist beforehand.
Possible side effects of antacids
Like all medicines, antacids can have side effects. Common side effects include:
feeling sick or vomiting
If you have diarrhoea or constipation after taking antacids it may be possible to switch to an alternative medicine. Speak to your GP or pharmacist for advice.
Any side effects you experience while taking antacids should pass once you stop taking the medication. Visit your GP if they continue.
Missed or extra doses
When taking antacid medicines, follow the instructions on the patient information leaflet that comes with the medicine or the advice of your GP or pharmacist.
If you miss a dose, it won't usually be necessary to alter your next dose. It's likely that you can carry on taking your normal dose. However, for specific advice about what to do, refer to the patient information leaflet that comes with your medicine.
Taking extra doses could cause several unpleasant side effects, such as nausea, vomiting, diarrhoea and constipation.
Who cannot take antacid medicines?
Antacids aren't suitable for everyone and sometimes they need to be taken with caution or avoided completely.
Use in children
Many antacid medicines aren't recommended for children under the age of 12.
Antacids containing calcium aren't recommended for long-term use in children because they can interfere with the rate that calcium is absorbed into the body and carried through the bloodstream. The right levels of calcium are vital for healthy bones and childhood development.
Prolonged use of antacids containing calcium can also lead to muscle weakness and cramps.
There have also been a number of cases linking the prolonged use of antacids containing magnesium and aluminium with rickets, a developmental disorder in infants that causes the bones to soften and weaken.
Always read the patient information leaflet (PIL) that comes with a medicine to ensure it's suitable for children. Check the correct dosage and seek advice from your GP or pharmacist about giving antacids to children under 12 years of age.
Use in pregnancy
Most types of antacids are considered to be safe to take during pregnancy. However, seek advice from your GP or pharmacist before taking antacids if you're pregnant or breastfeeding.
Use with other conditions
Sometimes, the use of some antacids isn't recommended if you have certain health conditions.
Speak to your GP or pharmacist if you have an existing health condition and are unsure whether antacids are suitable for you. You can also check the PIL that comes with all medication to ensure they're suitable for you.
Online copies of PILs can be found on the Medicines and Healthcare products Regulatory Agency (MHRA) and electronic Medicines Compendium (eMC) websites.
Use with other medicines
Taking antacids can sometimes interfere with your body’s ability to absorb other medications you may be taking. Therefore, you may be advised to stop taking other medication while you're taking antacids.
For example, you may not be able to take calcium supplements for a condition such as osteoporosis at the same time as some antacids. Antacids can also alter the effectiveness of some antibiotics.
However, it's important never to stop taking a medication prescribed for you without first consulting your GP or another suitably qualified healthcare professional.