They come as a liquid or chewable tablets and can be bought from pharmacies and shops without a prescription.
When antacids are used
Antacids may help if you have:
- indigestion ↗
- heartburn or acid reflux ↗ – also known as gastro-oesophageal reflux disease (GORD)
- a stomach ulcer ↗
- gastritis ↗ (inflammation of the stomach lining)
They can quickly relieve your symptoms for a few hours. But they don't treat the underlying cause and long-term use isn't recommended.
Speak to your GP if you find you need to take antacids regularly.
Common types of antacids
Many different types of antacid are available. Some are sold under a brand name and others are named after their main ingredient.
Ingredients to look for include:
- aluminium hydroxide
- magnesium carbonate
- magnesium trisilicate
- magnesium hydroxide
- calcium carbonate
- sodium bicarbonate
Some antacids also contain other medicines, such as an alginate (which coats your gullet with a protective layer) and simeticone (which reduces flatulence ↗).
How and when to take antacids
Check the instructions on the packet or leaflet to see how much antacid to take and how often. This depends on the exact medicine you're taking.
Antacids should be used when you have symptoms or think you will get them soon – for most people, the best time to take them is with or soon after meals, and just before going to bed.
Remember that doses for children may be lower than for adults.
Contact your GP or pharmacist, or call NHS 111 ↗, if you take too much of the medicine and start to feel unwell.
Taking antacids with food, alcohol and other medicines
It's best to take antacids with food or soon after eating because this is when you're most likely to get indigestion or heartburn.
The effect of the medicine may also last longer if taken with food.
Antacids can affect how well other medicines work, so don't take other medicines within two to four hours of taking an antacid.
You can drink alcohol while taking antacids, but alcohol can irritate your stomach and make your symptoms worse.
Side effects of antacids
Antacids don't usually have many side effects if they're only taken occasionally and at the recommended dose.
But sometimes they can cause:
These should pass once you stop taking the medicine.
Speak to a pharmacist or your GP if they don't improve or are troublesome. You may need to switch to another medicine.
Who may not be able to take antacids
Antacids are safe for most people to take, although they aren't suitable for everyone.
Speak to a pharmacist or your GP for advice first if you:
- are pregnant or breastfeeding – most antacids are considered safe to take while pregnant or breastfeeding, but always get advice first
- are looking for a medicine for a child under 12 years of age – some antacids are not recommended for children
- have liver disease ↗, kidney disease ↗ or heart failure ↗ – some antacids may not be safe if you have one of these problems
- have an illness that means you need to control how much salt (sodium) is in your diet, such as high blood pressure ↗ or cirrhosis ↗ (liver scarring) – some antacids contain high levels of sodium, which could make you unwell
- are taking other medicines – antacids can interfere with other medications and may need be avoided or taken at a different time