Ranitidine reduces the amount of acid your stomach makes.

It's used for indigestion and heartburn and acid reflux. It is also used for gastro-oesophageal reflux disease (GORD) - this is when you keep getting acid reflux. Ranitidine is also taken to prevent and treat stomach ulcers.

Sometimes, ranitidine is taken for a rare illness caused by a tumour in the pancreas or gut called Zollinger-Ellison syndrome.

Ranitidine comes as tablets, soluble (dispersible) tablets that dissolve in water to make a drink, or as a liquid that you drink.

All types of ranitidine are available on prescription. You can also buy the lowest strength 75mg tablets from pharmacies and supermarkets.

• It's usual to take ranitidine once or twice a day.
• Some people only need to take ranitidine for a short time, when they have symptoms. Others need to take it for longer.
• You can take ranitidine with or without food.
• It's unusual to get any side effects. However, some people may get stomach pain or constipation, or feel sick. This tends to get better as you carry on taking ranitidine.
• Ranitidine is called by the brand names Zantac, Zantac 75 and Zantac 75 Relief.

Ranitidine can be taken by adults. It can also be given to children under 16 years of age on prescription.

Ranitidine isn't suitable for some people. To make sure that it is safe for you, tell your doctor if you:

• have had an allergic reaction to ranitidine or any other medicines in the past
• have kidney problems
• have an intolerance to, or cannot absorb, some sugars such as fructose
• have been advised to eat a low calcium or low salt diet
• cannot have alcohol - ranitidine liquid contains a small amount of alcohol
• have phenylketonuria, a rare inherited illness

If you're due to have an endoscopy to find out what's causing your symptoms, stop taking ranitidine at least 2 weeks before your procedure. This is because ranitidine may hide some of the problems that would usually be spotted during an endoscopy.

It's usual to take ranitidine twice a day - 1 dose in the morning and 1 dose in the evening. Some people only need to take ranitidine once a day, at bedtime.

Very young babies, and people with Zollinger-Ellison syndrome, usually take ranitidine 3 times a day. People with severe inflammation of the food pipe (oesophagitis) may need to take it 4 times a day.

How to take it

You can take ranitidine with or without food. However, if you get symptoms whenever you eat or drink, take your medicine 30 minutes to 60 minutes before having a drink, snack or meal.

Tablets - swallow tablets whole with a glass of water, milk or juice.

Soluble tablets - dissolve tablets in half a glass of water. Do not use milk, fizzy water or other fizzy drinks. Wait until the medicine has completely dissolved and then drink it straight away.

Liquid - this comes with a syringe or spoon to help you measure it. If you don't have a syringe or spoon, ask your pharmacist for one. Do not use a kitchen teaspoon as it won't give you the right amount.

Liquid ranitidine is suitable for children and people who find it difficult to swallow tablets.

How much will I take?

Each tablet contains 75mg, 150mg or 300mg of ranitidine. You can buy 75mg tablets in pharmacies and supermarkets. Soluble tablets, and 150mg and 300mg tablets are only available on prescription.

The usual dose to treat:

• indigestion or heartburn is 75mg to 300mg a day
• stomach ulcers and inflammation of the food pipe is 300mg to 600mg a day
• Zollinger-Ellison syndrome is 450mg to 6 grams a day

Ranitidine liquid comes in 2 different strengths - your daily dose will depend on what your doctor prescribes. Follow your doctor's advice about how much ranitidine to take and when.

Doses are usually lower for children and people with kidney problems.

If a doctor prescribes ranitidine for your child, they will use your child's weight or age to work out the right dose.

Will my dose go up or down?

Sometimes your doctor will increase your dose of ranitidine if it isn't working well enough.

Depending on the reason you take ranitidine, you may take a higher dose to start with - usually for at least 1 month. After this, your doctor may recommend a lower dose.

How long will I take it for?

If you're taking lower strength ranitidine (75mg) that you bought from a pharmacy or supermarket, speak to a pharmacist or doctor before starting on a second packet. They may recommend tests to find out what's causing your symptoms, if taking ranitidine hasn't cleared them up.

If your doctor prescribes ranitidine for you, you may only need to take it for a few weeks or months, depending on your health problem. Sometimes you might need to take it for longer.

Your doctor may suggest taking ranitidine only when you have symptoms. This means you won't have to take it every day. Once you feel better, you can stop taking it - often after a few days or weeks.

Taking ranitidine this way isn't suitable for everyone. Speak to your doctor about what's best for you.

What if I forget to take it?

If you usually take it:

• once a day, take the missed dose as soon as you remember, unless it's less than 12 hours until your next dose - in which case skip the missed dose
• twice a day, take the missed dose as soon as you remember, unless it's nearly time for your next dose - in which case skip the missed dose
• 3 or 4 times a day, skip the missed dose and take your next dose as normal

Do not take a double dose to make up for a forgotten dose.

If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to remember your medicine.

What if I take too much?

Ranitidine is generally very safe. Taking too much is unlikely to harm you or your child.

If you take an extra dose by mistake, you might get some side effects, such as feeling sick. Call your doctor if you're worried, or you're bothered by side effects.

Most people who take ranitidine do not have any side effects. If you do get a side effect, it is usually mild and will go away when you stop taking ranitidine.

The following side effects aren't common and may happen in more than 1 in 1,000 people. Talk to your doctor or pharmacist if these side effects bother you or don't go away:

• stomach pains
• constipation
• feeling sick

Serious side effects

Serious side effects are very rare and happen in less than 1 in 10,000 people. Call a doctor straight away if you have:

• stomach pain that seems to be getting worse - this can be a sign of an inflamed liver or pancreas
• back pain, fever, pain when peeing or blood in your pee - these can be signs of kidney problems
• a rash, swollen joints or kidney problems - these can be signs that your small blood vessels are swollen (vasculitis)
• a slow or irregular heartbeat

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to ranitidine.

These are not all the side effects of ranitidine. For a full list see the leaflet inside your medicines packet.

What to do about:

• stomach pains - try to rest and relax. It can help to eat and drink slowly and have smaller and more frequent meals. Putting a heat pad or covered hot water bottle on your stomach may also help. If you are in a lot of pain, speak to your pharmacist or doctor.
• constipation - eat more high-fibre foods such as fresh fruit and vegetables and cereals, and drink plenty of water. Try to exercise, for example, by going for a daily walk or run. If this doesn't help, talk to your pharmacist or doctor.
• feeling sick - it may help if you don't eat rich or spicy food while you're taking ranitidine.

Usually, ranitidine is safe to take during pregnancy and while breastfeeding.

If you're pregnant, it's always better to try to treat indigestion without taking a medicine.

Your doctor or midwife will first advise you to try to ease your symptoms by eating smaller meals more often, and not eating fatty and spicy foods. They may also suggest raising the head of your bed by 10 to 20cm, so your head and chest are higher than your waist. This will help stop stomach acid travelling up towards your throat.

If these lifestyle changes don't work, you may be recommended a medicine like ranitidine.

Ranitidine and breastfeeding

Ranitidine is safe to take while you're breastfeeding. It passes into breast milk, but only in small amounts which aren't harmful to the baby.

However, if your baby is premature or has health problems check with your doctor first.

Some medicines can interfere with ranitidine and make you more likely to have side effects.

Tell your doctor if you're taking these medicines before you start taking ranitidine:

• anti-fungal medicines such as itraconazole, ketoconazole or posaconazole
• any medicine used to treat cancer
• HIV medicines

These are not all the medicines that may not mix well with ranitidine. For a full list see the leaflet inside your medicines packet.

Mixing ranitidine with herbal remedies and supplements

There isn't enough research to know if complementary medicines and herbal remedies are safe to take with ranitidine.