Cimetidine to reduce stomach acid
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Granskad av Sid DajaniSenast uppdaterad av Michael Stewart, MRPharmSLast updated 19 Jul 2023
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Cimetidine reduces the amount of acid produced in the stomach.
Any side-effects are usually mild and do not last long. The most common ones are diarrhoea, headache, dizziness and tiredness.
At a glance
Cimetidine is a medicine that reduces the amount of acid produced in your stomach.
It is used to treat stomach ulcers, acid reflux, heartburn, and indigestion.
You can take cimetidine before or after meals, exactly as prescribed by your doctor.
Side-effects can include diarrhoea, headache, muscle aches, dizziness or tiredness.
Discuss with your doctor if you have other medical conditions or are taking other medicines.
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About cimetidine
Typ av medicin | H2-receptor antagonist |
Används för | Treatment of conditions caused by too much acid being produced in the stomach. |
Även kallad | Tagamet® |
Tillgänglig som | Tabletter och flytande medicin för oral användning |
Cimetidine belongs to a group of medicines that reduce the amount of acid produced by the cells in the lining of the stomach. They are called 'histamine H2-receptor antagonists', but are commonly also called H2 blockers.
Cimetidine is helpful in the treatment of conditions caused by too much acid being produced in the stomach. These conditions include stomach ulcers (gastric ulcers), ulcers of the upper part of the intestine (duodenal ulcers), acid reflux or heartburn (reflux oesophagitis), and indigestion. It can also be used to treat stomach irritation and/or ulceration caused by non-steroidal anti-inflammatory drugs (NSAIDs).
Acid is produced naturally in your stomach to help to digest food. Excessive amounts of acid can irritate the lining of your stomach, causing inflammation, ulcers and other conditions. Cimetidine works by reducing the amount of acid produced by your stomach. This helps to relieve symptoms and assist the healing process where damage has already occurred.
Before taking cimetidine
Tillbaka till innehållTo make sure this is the right treatment for you, before you start taking cimetidine it is important that your doctor or pharmacist knows:
If you are pregnant, trying for a baby or breast-feeding.
If you have any of the following symptoms: difficulty swallowing, loss of blood, weight loss, or if you are being sick (vomiting).
If you have any problems with the way your liver works, or with the way your kidneys work.
Om du någonsin har haft en allergisk reaktion mot en medicin.
Om du tar några andra läkemedel. Detta inkluderar alla läkemedel du tar som finns att köpa utan recept, samt växtbaserade och komplementära läkemedel.
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How to take cimetidine
Tillbaka till innehållBefore you start this treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about cimetidine and will provide you with a full list of the side-effects which you may experience from taking it.
Take cimetidine exactly as your doctor tells you to. There are different strengths of tablets available - 200 mg, 400 mg, and 800 mg. You may be prescribed the tablets to take once, twice, or four times a day. Your doctor will tell you what dose is right for you and the directions will also be on the label of the pack to remind you what was said.
You can take cimetidine before or after meals.
If you forget to take a dose at your usual time, you can take it when you remember (unless it is nearly time for your next dose, in which case leave out the missed dose). Do not take two doses together to make up for a forgotten dose.
Få ut det mesta av din behandling
Tillbaka till innehållA course of treatment can vary in length, depending upon the reason why you are taking cimetidine. It may be just for a few days to relieve your symptoms, or for several weeks to help an ulcer heal. Keep any appointments that you have booked with your doctor so that your progress can be checked.
Some foods may make your symptoms worse. Foods and drinks that have been suspected of this include peppermint, tomatoes, chocolate, spicy foods, hot drinks, coffee, and alcoholic drinks. If it seems that a food is aggravating your symptoms, try avoiding it for a while to see if your symptoms improve. Also, try avoiding eating large meals, as these can make your symptoms worse too.
If you are overweight, it puts extra pressure on your stomach and encourages the symptoms of acid reflux. Losing some weight and eating a healthy balanced diet may help you.
Smoking increases the amount of acid produced by the stomach and may make your symptoms worse. If you are a smoker, speak with your doctor or pharmacist about how to quit.
If you buy any medicines 'over the counter', always check with a pharmacist that they are safe to take alongside your other medicines. Cimetidine can interfere with the way other medicines work.
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Can cimetidine cause problems?
Tillbaka till innehållAlong with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with cimetidine. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.
Common cimetidine side-effects (these affect fewer than 1 in 10 people) | Vad kan jag göra om jag upplever detta? |
Diarré | Drink plenty of water to replace lost fluids |
Headache, muscle aches | Drink plenty of water and ask your pharmacist to recommend a suitable painkiller. If the aches continue, let your doctor know. |
Feeling dizzy or tired | Do not drive and do not use tools or machines until you feel well again |
Skin rash | Om det är besvärligt, prata med din läkare |
Om du upplever några andra symtom som du tror kan bero på medicinen, tala med din läkare eller apotekare för vidare råd.
How to store cimetidine
Tillbaka till innehållFörvara alla läkemedel utom räckhåll och synhåll för barn.
Förvara på en sval, torr plats, borta från direkt värme och ljus.
Viktig information om alla läkemedel
Tillbaka till innehållViktig information om alla läkemedel
Ta aldrig mer än den föreskrivna dosen. Om du misstänker att du eller någon annan kan ha tagit en överdos av denna medicin, gå till akutmottagningen på ditt lokala sjukhus. Ta med behållaren, även om den är tom.
Denna medicin är för dig. Ge den aldrig till andra människor även om deras tillstånd verkar vara detsamma som ditt.
Om du ska genomgå en operation eller någon tandbehandling, informera den som utför behandlingen om vilka mediciner du tar.
Behåll inte föråldrade eller oönskade mediciner. Ta dem till ditt lokala apotek som kommer att ta hand om dem åt dig.
Om du har några frågor om denna medicin, fråga din apotekare.
Rapportera biverkningar av ett läkemedel eller vaccin
Om du upplever biverkningar kan du rapportera dem online via Yellow Card website.

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Vanliga frågor
What is cimetidine and how does it help with stomach issues?
Cimetidine is a medicine, also known as Tagamet, that reduces the amount of acid produced in your stomach. This helps treat conditions like stomach ulcers, duodenal ulcers, acid reflux (heartburn), and indigestion. By lowering acid levels, it eases symptoms and helps damaged areas heal.
Are there any specific symptoms I should tell my doctor about before starting cimetidine?
Yes, it's important to tell your doctor or pharmacist if you experience difficulty swallowing, have lost blood, lost weight without trying, or are experiencing vomiting. Also mention any liver or kidney problems, or if you've had an allergic reaction to any medicine before.
When is the best time to take cimetidine?
You can take cimetidine either before or after your meals. Your doctor will provide specific instructions on how often and at what dosage you should take it.
How long will I need to take cimetidine?
The length of your treatment with cimetidine can vary. It might be for only a few days to relieve immediate symptoms, or it could be for several weeks if you're dealing with an ulcer that needs time to heal. Your doctor will monitor your progress and advise on the duration.
Can certain foods make my stomach symptoms worse while taking cimetidine?
Yes, some foods and drinks might aggravate your symptoms. These include peppermint, tomatoes, chocolate, spicy foods, hot drinks, coffee, and alcoholic beverages. Eating large meals can also make symptoms worse. If you notice a food makes your symptoms worse, try avoiding it to see if you feel better. Losing weight and eating a healthy diet can also be beneficial.
What should I do if I forget to take a dose of cimetidine?
If you forget a dose, take it as soon as you remember. However, if it's almost time for your next scheduled dose, you should skip the missed dose and continue with your regular schedule. Do not take a double dose to make up for a forgotten one.
Can cimetidine affect other medicines I'm taking?
Yes, cimetidine can interfere with how other medicines work. If you are taking any other medicines, including those bought without a prescription, or herbal and complementary medicines, always inform your doctor or pharmacist. If you buy any new over-the-counter medicines, check with a pharmacist to ensure they are safe to take with cimetidine.
Vidare läsning och referenser
- Manufacturer's PIL, Cimetidine 200 mg/5 ml Oral Solution; Rosemont Pharmaceuticals Ltd, The electronic Medicines Compendium. Dated June 2020.
- Mediciner Komplett BNF 89:e Utgåvan; Brittiska Läkarföreningen och Kungliga Farmaceutiska Sällskapet i Storbritannien, London.
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About the authorView full bio

Michael Stewart, MRPharmS
Medicine Leaflet Review Manager – Contractor, Pharmacist
BPharm (Hons), MRPharmS
Michael is a community pharmacist practicing in the Midlands and South Yorkshire with more than 20 years’ experience advising on medicines and medical conditions. He has a strong background in healthcare training, having produced and delivered training courses for pharmacy teams and staff of residential care settings, including nurses. He has also contributed to pharmacy advisory boards for the management of low acuity conditions in the community.
About the reviewer

Sid Dajani
Sultan Dajani qualified at the London School of Pharmacy in 1994 and became the youngest elected member of the Royal Pharmaceutical Society council since its founding in 1842.
Artikelhistorik
Informationen på denna sida är skriven och granskad av kvalificerade kliniker.
Next review due: 18 Jul 2026
19 Jul 2023 | Senaste versionen

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