Metformin Hydrochloride 500 mg film-coated tablets – patient leaflet, side effects, dosage

1. WHAT METFORMIN TABLETS IS AND WHAT IT IS USED

These tablets are available in two different strengths and your doctor will decide which strength is most suitable for you. Each tablet contains either 500 mg or 850 mg of the active ingredient, metformin hydrochloride.

Metformin hydrochloride belongs to a group of medicines called oral hypoglycaemics, which works by reducing the level of sugar in the blood.

Metformin Tablets are used for the treatment of a type of diabetes which usually only occurs in adults and is not severe enough to need insulin, but which does not respond to dietary measures alone. In some patients metformin may be used in combination with other anti-diabetic medicines called sulphonylureas.

2. WHAT YOU NEED TO KNOW BEFORE YOU TAKE METFORMIN TABLETS

Do not take Metformin Tablets

• If you know you are allergic to metformin or to any of the other ingredients (these are listed in section 6)
• If you have failed to respond to treatment with other antidiabetic medicines called sulphonylureas
• If you have ever fainted or ever suffered a coma from having diabetes
• If you have uncontrolled diabetes, with symptoms such as severe hyperglycaemia (high blood glucose), nausea, vomiting, dehydration, rapid weight loss, lactic acidosis (see “Risk of lactic acidosis” below) or ketoacidosis, Ketoacidosis is a condition in which substances called ‘ketone bodies’ accumulate in the blood and which can lead to diabetic pre-coma. Symptoms include stomach pain, fast and deep breathing, sleepiness or unusual fruity odour of the breath
• If you have problems with your liver
• If you have severely reduced kidney function.
• If you have an acute or chronic disease which could cause decreased oxygen supply (hypoxia), like heart failure, respiratory failure or a recent heart attack or you have breathing problems. This may lead to a decrease in oxygen supply to tissue which can put you at risk for lactic acidosis (see 'Warnings and precautions') • If you are pregnant or think you may be pregnant
• If you suffer from alcoholism or acute alcohol intoxication • If you have any problems with your circulation for example, frequent cramp in your calves or leg ulcers that do not heal • If you have a severe infection, fever, or if you are suffering from shock or trauma or are unwell in any other way. Severe infections may lead to kidney problems, which can put you at risk for lactic acidosis (see 'Warnings and precautions')
• If you suffer from an inflamed pancreas (pancreatitis) • If you are on a special low calorie diet (less than 1000 calories per day or 4200 KJ per day)
• If you are dehydrated (feeling extremely thirsty) or suffer from severe diarrhoea or you have vomited several times in a row. Dehydration may lead to kidney problems, which can put you at risk for lactic acidosis

You must check with your doctor before taking these tablets if you are breast-feeding.

Other special warnings

• If you are going to have an operation requiring an anaesthetic or you are to undergo a scan requiring injection of a dye, you must ensure the doctor in charge is aware you are taking Metformin Tablets (as they will need to be stopped up to 48 hours before the procedures)
• You should not drink alcohol while taking Metformin Tablets • Patients who are already on insulin should only be started on a course of treatment with metformin in a hospital

• If you are taking these tablets continuously, your doctor will perform regular blood tests to check your Vitamin B12 levels and

  your kidney function

  • If you are an elderly patient (approximately over the age of 65 years) your doctor will perform blood and urine tests to check your kidney function before starting Metformin If any of the conditions above apply to you, please discuss your treatment with your doctor before taking this medicine.

Warnings and precautions

Risk of lactic acidosis

Metformin may cause a very rare, but very serious side

effect called lactic acidosis, particularly if your kidneys are not working properly. The risk of developing lactic acidosis is also increased with uncontrolled diabetes, serious infections, prolonged fasting or alcohol intake, dehydartaion (see further information below) liver problems and any medical conditions in which a part of the body has a reduced supply of oxygen (such as acute severe heart disease).

If any of the above apply to you, talk to your doctor for further instructions.

Stop taking Metformin for a short time if you have a condition that may be associated with dehydration

(significant loss of body fluids) such as severe vomiting, diarrhoea, fever, exposure to heat or if you drink less fluid than normal. Talk to your doctor for further instructions.

Stop taking Metformin and contact a doctor or the nearest hospital immediately if you experience some of the symptoms of lactic acidosis, as this conditions may lead to coma.

Symptoms of lactic acidosis include:

• vomiting
• stomach ache (abdominal pain)
• muscle cramps
• a general feeling of not being well with severe tiredness • difficulty in breathing
• reduced body temperature and heartbeat

Lactic acidosis is a medical emergency and must be treated in a hospital.

Talk to your doctor promptly for further instructions if: • You are known to suffer from a genetically inherited disease affecting mitochondria (the energy-producing components within cells) such as MELAS syndrome (Mitochondrial Encephalopathy, myopathy, Lactic acidosis and Stroke-like episodes) or Maternal inherited diabetes and deafness (MIDD).

• You have any of these symptoms after starting metformin: seizure, declined cognitive abilities, difficulty with body movements, symptoms indicating nerve damage (e.g. pain or numbness), migraine and deafness.

If you need to have major surgery you must stop taking Metformin tablets during surgery and for some time after the procedure. Your doctor will decide when you must stop and when to restart your treatment with Metformin.

Metformin on its own does not cause hypoglycaemia (a blood glucose level which is too low). However, if you take metformin together with other medicines to treat diabetes that can cause hypoglycaemia (such as sulphonylureas, insulin, meglitinides), there is a risk of hypoglycaemia. If you experience symptoms of hypoglycaemia such as weakness, dizziness, increased sweating, fast heart beating, visions disorders or difficulty in concentration, it usually helps to eat or drink something containing sugar.

During treatment with Metformin, your doctor will check your kidney function at least once a year or more frequently if you are elderly and/or if you have worsening kidney function.

Other medicines and Metformin Tablets

If you need to have an injection of a contrast medium that contains iodine into your bloodstream, for example in the context of an X-ray or scan, you must stop taking Metformin Tablets before or at the time of the injection. Your doctor will decide when you must stop and when to restart your treatment with Metformin.

Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines. You may need more frequent blood glucose and kidney functions tests or your doctor may need to adjust the dosage of Metformin. It is especially important to mention the following:

• Medicines which increase urine production (diuretics) • Medicines used to treat pain and inflammation (NSAID and COX-2-inhibitors, such as ibuprofen and celecoxib) • Certain medicines for the treatment of high blood pressure (ACE inhibitors and angiotensin II receptors antagonists) Metformin Tablets and other medicines you may be taking may interact with each other. Make sure your doctor knows if you are taking any of the following:
• Insulin, other anti-diabetic drugs and guar
• Monoamine-oxidase inhibitors (MAOI’s) or other medicines to treat depression or psychosis such as chlorpromazine
• Aspirin or any other non-steroidal medicines for pain and inflammation
• ACE inhibitors and beta-blockers for high blood pressure • Other medicines for high blood pressure eg. Clonidine reserpine, guanethidine or diazoxide
• Thiazides and loop diuretics (water tablets)
• Beta-2 agonists such as salbutamol or terbutaline (used to treat asthma)
• Medicines for lowering cholesterol in the blood such as clofibrate or nicotinic acid derivatives
• Cyclophosphamide (to control inflammation)
• Cimetidine (to treat stomach ulcers)
• Hormone drugs such as the contraceptive pill or hormone replacement therapy (HRT)
• Steroids such as prednisolone or hydrocortisone
• Oxytetracycline (an antibiotic to treat infections)
• Phenprocoumon (an anticoagulant to thin the blood) • Adrenaline and other sympathomimetics (used to treat allergic conditions and heart attacks)
• Glucagon (used to control low blood sugar levels) • Thyroid hormones such as thyroxine
• Medicines that may change the amount of Metformin tablets in

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your blood, especially if you have reduced kidney function (such as verapamil, rifampicin, cimetidine, dolutegravir, ranolazine, trimethoprime, vandetanib, isavuconazole, crizotinib, olaparib). • Other medicines used to treat diabetes.

Always tell your doctor or pharmacist about all the medicines you are taking. This means medicines you have bought yourself as well as those you have on prescription from your doctor.

Metformin Tablet with Alcohol

Avoid excessive alcohol intake while taking Metformin since this may increase the risk of lactic acidosis (see section “Warnings and Precautions”).

Pregnancy and breast-feeding

During pregnancy, you need insulin to treat your diabetes. Tell your doctor if you are, you think you might be or are planning to become pregnant, so that he or she may change your treatment or monitoring of your blood glucose levels. This medicine is not recommended if you are breast-feeding or if you are planning to breast-feed your baby.

Driving and using machines

Metformin Tablets taken on their own should not affect your ability to drive or operate machinery but if you are also taking them with another medicine (sulphonylureas or insulin) to lower blood sugar levels, it is possible the combined effect of these medicines may make some patients feel faint or dizzy.

If this happens, do not drive or operate machinery until you feel better.

Metformin tablet contains Sodium:

This medicine contains less than 1 mmol sodium (23 mg) per tablet, that is to say essentially ‘sodium-free’.

3. HOW TO TAKE METFORMIN TABLETS

Always take this medicine exactly as your doctor or pharmacist has told you. Check with your doctor or pharmacist if you are not sure. The tablets should be swallowed whole with a glass of water during or after meals.

The doctor will decide what dose you need to take. Always take the tablets exactly as the doctor has told you. The dose will be on the pharmacist's label. If you are not sure, ask your doctor or pharmacist.

Carry on taking them for as long as you have been told unless you have any problems. In that case, check with your doctor.

The recommended dose for adults is: One or two 500 mg tablets, or one 850 mg tablet each day. The dose will be gradually increased by your doctor until the right dose to control your symptoms is found. In most cases symptoms can be eventually controlled with three 500 mg tablets or two 850 mg tablets each day in divided doses. The maximum daily doses are six 500 mg tablets or three 850 mg tablets.

If you have reduced kidney function, your doctor may prescribe a lower dose.

Use in children 10 years and over and adolescents:

Usually start with 500 mg or 850 mg Metformin tablet once a day. The maximum daily dose is 2000 mg taken as 2 or 3 divided doses. Treatment of children between 10 and 12 years of age is only recommended on specific advice from your doctor, as experience in this age group is limited.

Monitoring

• Your doctor will perform regular blood glucose tests and will adapt your dose of metformin to your blood glucose levels. Make sure that you talk to your doctor regularly.

This is particularly important for children and adolescents or if you are an older person.

• Your doctor will also check at least once a year how well your kidneys work. You may need more frequent checks if you are an elder person or if your kidneys are not working normally.

If you take more Metformin Tablets than you should

If you have taken more metformin than you should have, you may experience lactic acidosis. Symptoms of lactic acidosis are non-specific such as vomiting, stomach pain (abdominal pain) with muscle cramps, a general feeling of not being well with severe tiredness and difficulty in breathing. Further symptoms are reduced body temperature and heart beat. If you experience some of these symptoms you should immediately seek medical attention, as lactic acidosis may lead to coma. Stop taking Metformin immediately and contact a doctor or the nearest hospital straight away.

If you forget to take Metformin Tablets

If you miss a dose, take the missed dose as soon as you remember unless it is nearly time for your next dose. Do not take a double dose to make up for the forgotten dose.

4. POSSIBLE SIDE EFFECTS

Like all medicines, Metformin Tablets can cause side effects, although not everybody gets them. Metformin may cause a very rare

(may effect upto one user in 10,000), but very serious side effects called lactic acidosis (see sections “Warning and precautions”). If this happens happens you must stop taking Metformin Tablets and contact a doctor or the nearest hospital immediately, as lactic acidosis may lead to coma.

The most common side effects (usually when you first start taking metformin) are:

Very common side effects (in more than 1 in 10 people)

• digestive problems, such as feeling sick (nausea), being sick (vomiting), diarrhoea, bellyache (abdominal pain), metallic taste and loss of appetite. These side effects most often happen at the beginning of the treatment with metformin. It helps if you spread the doses over the day and if you take metformin with or straight after a meal. If symptoms continue, stop taking metformin and talk to your doctor.

• decreased or low vitamin B12 levels in the blood

  (symptoms may include extreme tiredness (fatigue), a sore and red tongue (glossitis), pins and needles (paraesthesia) or pale or yellow skin). Your doctor may arrange some tests to find out the cause of your symptoms because some of these may also be caused by diabetes or due to other unrelated health problems.

Very rare side effects (in less than 1 in 10,000 people)

• lactic acidosis. This is a very rare but serious complication particularly if your kidneys are not working properly.

Symptoms of lactic acidosis are non-specific (see section ‘Warning and precautions’)

If these side-effects occur they usually get better spontaneously so you should continue to take the tablets unless your stomach upset is severe or shows no signs of getting better after a few days - in this case contact your doctor.

Very rarely (in less than 1 in 10,000 people)

• liver disorders such as inflammation of the liver may occur or blood tests to check your liver may have abnormal results. This may cause tiredness, loss of appetite, weight loss, with or without yellowing of the skin or whites of the eyes. If this happens to you, stop taking metformin and talk to your doctor.
• skin reactions such as redness, itching or hives or allergic reactions may occur. If you notice a rash ask your doctor for advice about continuing to take the tablets.

Additional side effects in children and adolescents

Limited data in children and adolescents showed that adverse events were similar in nature and severity to those reported in adults.

Reporting of side effects

If you get any side effects, talk to your doctor or pharmacist. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via Yellow Card Scheme, at www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects you can help provide more information on the safety of this medicine.

5. HOW TO STORE METFORMIN TABLETS

Keep out of the sight and reach of children - preferably in a locked cupboard or cabinet.

Do not store above 25°C. Store the tablets in the original blister pack.

Do not take the tablets after the expiry date shown on the carton. The expiry date refers to the last day of that month. If your doctor tells you to stop taking the tablets, please take any unused medicine back to your pharmacist to be destroyed.

Do not throw away any medicines via wastewater.

Ask your pharmacist how to throw away medicines you no longer use. These measures will help to protect the environment.

6. CONTENTS OF THE PACK AND OTHER INFORMATION

What Metformin Tablet contain

Each tablet contains either 500 mg or 850 mg of the active ingredient, metformin hydrochloride. The tablets also contain sodium starch glycollate, maize starch, povidone, colloidal anhydrous silica, magnesium stearate, hypromellose, titanium dioxide (E171), propylene glycol, macrogol 6000 and purified talc.

What Metformin Tablets look like and contents of the pack.

Metformin Tablets are round, white, film-coated tablets. The 500 mg strength tablets are marked with "500" on one side and the 850 mg strength tablets are marked with "850" on one side. They are available in blister packs (PVC/PVDC/Al or PVC/Al) containing 28, 56, 60 or 84 tablets (500 mg) and 28, 42, 56 or 84 tablets (850 mg). Not all pack sizes may be marketed.

POM

Marketing Authorisation Holder

Lyrus Life Sciences Limited,

C/O Thakur-Chabert 7a Vine Street

Uxbridge

United Kingdom

UB8 1QE

Manufacturer

Aspire Pharma Limited

Unit 4, Rotherbrook Court, Bedford Road,

Petersfield, GU32 3QG, United Kingdom

The leaflet was last revised in July 2026

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