What antacids are used for
Antacids are medicines that neutralise acid already present in the stomach. They come as chewable tablets, liquids and powders, and usually contain aluminium hydroxide, magnesium hydroxide, calcium carbonate, sodium bicarbonate or a mix. Many also contain simethicone, which helps release trapped gas.
People use antacids for occasional heartburn, sour burps, indigestion and a burning feeling in the upper tummy, often after heavy, spicy or oily meals, festive feasts or late dinners. They relieve symptoms quickly but do not heal ulcers or treat the cause of repeated acidity.
- Occasional heartburn and acid reflux
- Indigestion and a burning upper stomach
- Bloating and gas, when combined with simethicone
- Short-term relief while other treatment starts working
How antacids work
Stomach acid is strong, and when it rises into the food pipe or irritates the stomach lining, it causes burning pain. Antacids are mild alkaline substances that react with the acid and neutralise it, so the burning settles, often within minutes.
Their effect is short, lasting a few hours at most, because the stomach keeps making new acid. This is different from medicines like pantoprazole, omeprazole or famotidine, which reduce how much acid is made and are used when acidity is frequent or when ulcers need healing.
Antacids side effects: common and serious
Side effects depend on the ingredient. Magnesium-based antacids can cause loose stools, while aluminium- and calcium-based ones can cause constipation. Many products combine magnesium and aluminium to balance these effects. Sodium bicarbonate and calcium carbonate can cause burping and bloating.
Serious problems are uncommon with occasional use. Frequent or heavy use can upset the body's mineral balance, causing high magnesium, high calcium or low phosphate levels, especially in people with kidney disease. Sodium-containing antacids add salt, which matters for people with high blood pressure or heart failure. Heavy calcium intake can contribute to kidney stones.
Who should take extra care with antacids
People with kidney disease should avoid regular antacid use unless a doctor advises, as magnesium and aluminium can build up in the body. People on a low-salt diet for blood pressure, heart failure or liver disease should avoid sodium bicarbonate products. Elderly people are more likely to get constipation or mineral imbalances.
Heartburn is common in pregnancy, and some antacids are considered suitable, but ask your doctor which one to use. Antacids are not usually given to young children without a doctor's advice. Anyone over middle age with new or changing indigestion should see a doctor rather than relying on antacids.
Antacids interactions to know
Antacids can stop other medicines from being absorbed properly. These include some antibiotics such as ciprofloxacin, doxycycline and azithromycin, thyroid medicine levothyroxine, iron tablets, some HIV medicines and certain heart medicines. A gap of a few hours between antacids and these medicines is usually advised; ask your pharmacist how long the gap should be for your medicines.
Some enteric-coated tablets, which are designed to dissolve further down the gut, may dissolve too early if taken with antacids. Always tell your pharmacist you use antacids when collecting a new prescription. This simple step helps avoid a medicine quietly failing to work, which can be serious with antibiotics or thyroid treatment.
Practical tips for using antacids
Follow the label or your pharmacist's advice on how much to take. Antacids often work best when taken after meals or at bedtime, when symptoms usually appear. Shake liquids well before use and chew tablets thoroughly. Do not use them for longer than the label says without asking a doctor, and choose a product without sodium if you have high blood pressure.
Reduce the need for antacids by eating smaller, regular meals, not skipping breakfast, avoiding lying down soon after food, cutting back on fried and very spicy food, tea, coffee, alcohol and smoking, and keeping a healthy weight. If you find yourself needing antacids most days for more than two weeks, see a doctor.
- Keep a gap between antacids and other medicines
- Choose low-sodium products if you have BP or heart problems
- Do not use them to hide symptoms that keep coming back
When to talk to your doctor about antacids
See a doctor if acidity is frequent, wakes you at night, or does not improve with antacids and lifestyle changes. Get urgent help for black stools, vomiting blood, difficulty swallowing, weight loss or chest pain, which should never be assumed to be gas. Ask your doctor or pharmacist before using antacids regularly or with other medicines.
Related medicines
Only your doctor can decide which medicine, dose and combination is right for you.
- Proton pump inhibitors such as pantoprazole or omeprazoleStrongly reduce acid production for GERD and ulcers.Long-term use should be reviewed by a doctor.
- Famotidine (H2 blocker)Lowers acid production for several hours.Use as the label or your doctor advises.
- Alginate liquidsForm a raft on stomach contents to reduce reflux.May contain sodium or calcium.
- SimethiconeHelps break up gas bubbles to ease bloating.Does not reduce acid.
See a doctor urgently if
- Chest pain, especially with sweating, breathlessness or pain spreading to the arm or jaw
- Black stools or vomiting blood
- Difficulty swallowing or food getting stuck
- Unexplained weight loss or persistent vomiting
- Needing antacids most days for more than two weeks
Tests that may help
This article is general health information, not medical advice. Do not start, stop or combine medicines on your own — always follow your doctor's prescription and ask your pharmacist if unsure.