Patient leaflets and SmPCs, drug interaction checker, official and paediatric dosages, pregnancy and breastfeeding guidance, and NHS pharmacy opening hours — all in one place.
Patient leaflets and SmPCs, drug interaction checker, official and paediatric dosages, pregnancy and breastfeeding guidance, and NHS pharmacy opening hours — all in one place.
Metformin 500 mg and 850 mg contain metformin, a medicine to treat diabetes. It belongs to a group of medicines called biguanides.
Insulin is a hormone produced by the pancreas that makes your body take in glucose (sugar) from the blood. Your body uses glucose to produce energy or stores it for future use.
If you have diabetes, your pancreas does not make enough insulin or your body is not able to use properly the insulin it produces. This leads to a high level of glucose in your blood. Metformin helps to lower your blood glucose to as normal a level as possible.
If you are an overweight adult, taking Metformin over a long period of time also helps to lower the risk of complications associated with diabetes. Metformin is associated with either a stable body weight or modest weight loss.
Metformin is used to treat patients with type 2 diabetes (also called 'non-insulin dependent diabetes') when diet and exercise alone have not been enough to control your blood glucose levels. It is used particularly in overweight patients.
Adults can take Metformin on its own or together with other medicines to treat diabetes (medicines taken by mouth or insulin).
Children 10 years and over and adolescents can take Metformin on its own or together with insulin.
Do not take Metformin if you: • are allergic to metformin or any of the other ingredients of this medicine (listed in section 6).
• have liver problems.
• have severely reduced kidney function.
• have uncontrolled diabetes, with, for example, severe hyperglycaemia (high blood glucose), nausea, vomiting, diarrhoea, 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 your breath developing an unusual fruity smell.
• lost too much water from your body (dehydration), due to long-lasting or severe diarrhoea, or if you have vomited several times in a row. Dehydration may lead to kidney problems, which can put you at risk for lactic acidosis (see 'Warnings and precautions').
• have a severe infection, such as an infection affecting your lungs or bronchial system or your kidneys. Severe infections may lead to kidney problems, which can put you at risk for lactic acidosis (see 'Warnings and precautions').
• are treated for acute heart failure or have recently had a heart attack, have severe problems with your circulation (such as shock) or have breathing difficulties. This may lead to a lack in oxygen supply to tissue which can put you at risk for lactic acidosis (see 'Warnings and precautions').
• drink a lot of alcohol.
If any of the above applies to you, talk to your doctor, before you start taking this medicine.
Make sure you ask your doctor for advice, if you:
• need to have an examination such as X-ray or scan involving the injection of contrast medicines that contain iodine into your bloodstream.
• need to have major surgery.
You must stop taking Metformin for a certain period of time before and after the examination or the surgery. Your doctor will decide whether you need any other treatment for this time. It is important that you follow your doctor's instructions precisely.
Warnings and precautions Talk to your doctor or pharmacist before taking Metformin.
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, dehydration (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 diseases).
If any of the above apply to you, talk to your doctor for further instructions.
It is important for you to comply with your medication intake, dietary instructions and regular exercise program because this can reduce the risk of lactic acidosis.
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 condition 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.
If you need to have major surgery you must stop taking Metformin during and for some time after the procedure. Your doctor will decide when you must stop and when to restart your treatment with Metformin.
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.
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.
Other medicines and Metformin Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines.
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.
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 before or at the time of the injection. Your doctor will decide when you must stop and when to restart your treatment with Metformin.
You may need more frequent blood glucose and kidney function 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 (NSAIDs and COX-2-inhibitors, such as ibuprofen and celecoxib).
• certain medicines for the treatment of high blood pressure (ACE inhibitors and angiotensin II receptor antagonists).
• beta-2 agonists such as salbutamol or terbutaline (used to treat asthma).
• corticosteroids (used to treat a variety of conditions, such as severe inflammation of the skin or in asthma).
• medicines that may change the amount of Metformin in your blood, especially if you have reduced kidney function (such as verapamil, rifampicin, cimetidine, dolutegravir, ranolazine, trimethoprim, vandetanib, isavuconazole, crizotinib, olaparib).
• other medicines used to treat diabetes.
Metformin 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 If you are pregnant or breast-feeding, think you may be pregnant or are planning to have a baby, ask your doctor or pharmacist for advice before taking this medicine. During pregnancy, you need insulin to treat your diabetes instead of Metformin.
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 on its own does not cause hypoglycaemia (a blood glucose level which is too low). This means that it will not affect your ability to drive or use machines.
However, take special care if you take Metformin together with other medicines to treat diabetes that can cause hypoglycaemia (such as sulphonylureas, insulin, meglitinides). Symptoms of hypoglycaemia include weakness, dizziness, increased sweating, fast heartbeat, vision disorders or difficulty in concentration. Do not drive or use machines if you start to feel these symptoms.
Always take this medicine exactly as your doctor or pharmacist has told you. Check with your doctor or pharmacist if you are not sure.
Metformin cannot replace the benefits of a healthy lifestyle. Continue to follow any advice about diet that your doctor has given you and get some regular exercise.
Recommended dose Children 10 years and over and adolescents usually start with 500 mg or 850 mg metformin 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.
Adults usually start with 500 mg or 850 mg metformin two or three times a day. The maximum daily dose is 3000 mg taken as 3 divided doses.
If you have reduced kidney function, your doctor may prescribe a lower dose.
If you take insulin too, your doctor will tell you how to start Metformin.
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 older person or if your kidneys are not working normally.
How to take Metformin Take Metformin with or after a meal. This will avoid you having side effects affecting your digestion.
Do not crush or chew the tablets. Swallow each tablet with a glass of water.
If you:
• Take one dose a day, take it in the morning (breakfast).
• Take two divided doses a day, take them in the morning (breakfast) and evening (dinner).
• Take three divided doses a day, take them in the morning (breakfast), at noon (lunch) and in the evening (dinner).
If, after some time, you think that the effect of Metformin is too strong or too weak, talk to your doctor or pharmacist.
500 and 850 mg: The score line is only there to help. you break the tablet if you have difficulty swallowing it whole.
If you take more Metformin 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, bellyache (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 heartbeat. If you experience some of these symptoms, you should seek immediate 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 Do not take a double dose to make up for a forgotten dose. Take the next dose at the usual time.
If you have any further questions on the use of this medicine, ask your doctor or pharmacist.
Like all medicines, this medicine can cause side effects, although not everybody gets them.
The following side effects may occur:
If the following side effects occur, you should stop taking Metformin and contact a doctor or the nearest hospital immediately: • Metformin may cause a very rare (may affect up to 1 in 10,000 people), but very serious side effect called lactic acidosis (see section "Warnings and precautions"). If this happens you must stop taking Metformin and contact a doctor or the nearest hospital immediately, as lactic acidosis may lead to coma.
• digestive problems, such as feeling sick (nausea), being sick (vomiting), diarrhoea, bellyache (abdominal pain) and loss of appetite are very common (may affect more than 1 in 10 people). 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.
• abnormalities in liver function tests or hepatitis (inflammation of the liver; this may cause tiredness, loss of appetite, weight loss, with or without yellowing of the skin or whites of the eyes) are very rare (may affect up to 1 in 10,000 people). If this happens to you, stop taking Metformin and talk to your doctor.
Other side effects may include the following: Common side effects (may affect up to 1 in 10 people)
• changes in taste.
• 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 (may affect up to 1 in 10,000 people)
• skin reactions such as redness of the skin. (erythema), itching or an itchy rash (hives).
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 the 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.
Keep this medicine out of the sight and reach of children. If a child is treated with Metformin, parents and caregivers are advised to oversee how this medicine is used.
Do not use this medicine after the expiry date which is stated on the carton or the blister after 'EXP'.
The expiry date refers to the last day of that month.
This medicinal product does not require any special storage conditions.
Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help protect the environment.
What Metformin 500 mg or 850 mg contains The active substance is metformin hydrochloride.
• One film-coated tablet of Metformin 500 mg contains 500 mg metformin hydrochloride corresponding to 390 mg metformin base.
• One film-coated tablet of Metformin 850 mg contains 850 mg metformin hydrochloride corresponding to 662.9 mg metformin base.
• The other ingredients are povidone (K-25), magnesium stearate, hypromellose (5 mPas), Macrogol 6000, Titanium dioxide (E 171), Talc.
What Metformin looks like and contents of the pack Metformin 500 mg film-coated tablets are white to off-white, oval film-coated tablets with break mark on one face. The tablets are supplied in blister packs of 28, 84 or 500 tablets.
Metformin 850 mg film-coated tablets are white to off-white, oblong film-coated tablets with break mark on both faces. The tablets are supplied in blister packs of 56 or 300 tablets.
Not all pack sizes may be marketed.
Marketing Authorization Holder Flamingo Pharma (UK) Ltd.
1st Floor
Kirkland House
11-15 Peterborough Road
Harrow
Middlesex
HA1 2AX
United Kingdom
Manufacturer Flamingo Pharma (UK) Limited
The Bloc
38 Springfield Way
Anlaby
Hull
HU10 6RJ
United Kingdom
The Leaflet was last revised in March 2025.
Product licence number
PL 43461/0118
PL 43461/0119
Flamingo Pharma (UK) Ltd
Address
The BLOC, 38 Springfield Way, Kingston Upon Hull, HU10 6RJ, UK
Telephone
+44 (0) 7784240228
Medical Information Direct Line
+44 8000668348
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http://www.flamingopharma.co.uk
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Metformin 850 mg film-coated tablets comes as tablet containing 850mg. Always follow the dose your doctor or pharmacist has given you, and read the leaflet that comes with the medicine.
The active substance in Metformin 850 mg film-coated tablets is metformin hydrochloride.
Medicines with the same active substance, strength and form include: Glucophage 850 mg film coated tablets, Glucophage SR 850 mg prolonged release tablets, Metformin 850 mg film coated Tablets. They are interchangeable only if your prescriber or pharmacist says so.
This leaflet reproduces the patient information leaflet approved for Metformin 850 mg film-coated tablets, as published on the electronic medicines compendium (emc). The version printed inside your medicine’s packaging is the one that applies to you.
Whether a medicine is available over the counter or on prescription only depends on its licence. Check the leaflet, or ask your pharmacist — they can tell you straight away.
The text above reproduces the patient information leaflet approved for this medicine, restructured for easier reading.
Treatment of type 2 diabetes mellitus, particularly in overweight patients, when dietary management and exercise alone does not result in adequate glycaemic control.
• In adults, Metformin may be used as monotherapy or in combination with other oral anti-diabetic agents or with insulin.
• In children from 10 years of age and adolescents, Metformin may be used as monotherapy or in combination with insulin.
A reduction of diabetic complications has been shown in overweight type 2 diabetic adult patients treated with metformin as first-line therapy after diet failure (see section 5.1).
Posology
Adults with normal renal function (GFR ≥ 90 mL/min)
Monotherapy and combination with other oral antidiabetic agents
The usual starting dose is 500 mg or 850 mg metformin hydrochloride 2 or 3 times daily given during or after meals.
After 10 to 15 days the dose should be adjusted on the basis of blood glucose measurements. A slow increase of dose may improve gastrointestinal tolerability.
The maximum recommended dose of metformin hydrochloride is 3 g daily, taken as 3 divided doses.
If transfer from another oral antidiabetic agent is intended: discontinue the other agent and initiate metformin at the dose indicated above.
Combination with insulin
Metformin and insulin may be used in combination therapy to achieve better blood glucose control. Metformin hydrochloride is given at the usual starting dose of 500 mg or 850 mg 2 or 3 times daily, while insulin dosage is adjusted on the basis of blood glucose measurements.
Elderly
Due to the potential for decreased renal function in elderly subjects, the metformin dosage should be adjusted based on renal function. Regular assessment of renal function is necessary (see section 4.4).
Renal impairment
A GFR should be assessed before initiation of treatment with metformin containing products and at least annually thereafter. In patients at an increased risk of further progression of renal impairment and in the elderly, renal function should be assessed more frequently, e.g. every 3 – 6 months.
GFR
mL/min
Total maximum daily dose
(to be divided into 2 – 3 daily doses)
Additional considerations
60 – 89
3000 mg
Dose reduction may be considered in relation to declining renal function.
45 – 59
2000 mg
Factors that may increase the risk of lactic acidosis (see section 4.4) should be reviewed before considering initiation of metformin.
The starting dose is at most half of the maximum dose.
30 – 44
1000 mg
< 30
-
Metformin is contraindicated.
Paediatric population
Monotherapy and combination with insulin
• Metformin can be used in children from 10 years of age and adolescents.
• The usual starting dose is 500 mg or 850 mg metformin hydrochloride once daily, given during or after meals.
After 10 to 15 days the dose should be adjusted on the basis of blood glucose measurements. A slow increase of dose may improve gastrointestinal tolerability. The maximum recommended dose of metformin hydrochloride is 2 g daily, taken as 2 or 3 divided doses.
Method of administration
For oral use.
• Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.
• Any type of acute metabolic acidosis (such as lactic acidosis, diabetic ketoacidosis).
• Diabetic pre-coma.
• Severe renal failure (GFR < 30 mL/min).
• Acute conditions with the potential to alter renal function such as: dehydration, severe infection, shock.
• Disease which may cause tissue hypoxia (especially acute disease, or worsening of chronic disease) such as: decompensated heart failure, respiratory failure, recent myocardial infarction, shock.
• Hepatic insufficiency, acute alcohol intoxication, alcoholism.
Lactic acidosis
Lactic acidosis, a very rare, but serious metabolic complication, most often occurs at acute worsening of renal function or cardiorespiratory illness or sepsis. Metformin accumulation occurs at acute worsening of renal function and increases the risk of lactic acidosis.
In case of dehydration (severe diarrhoea or vomiting, fever or reduced fluid intake), metformin should be temporarily discontinued and contact with a health care professional is recommended.
Medicinal products that can acutely impair renal function (such as antihypertensives, diuretics and NSAIDs) should be initiated with caution in metformin-treated patients. Other risk factors for lactic acidosis are excessive alcohol intake, hepatic insufficiency, inadequately controlled diabetes, ketosis, prolonged fasting and any condition associated with hypoxia, as well as concomitant use of medicinal products that may cause lactic acidosis (see sections 4.3 and 4.5).
Patients and/or care-givers should be informed of the risk of lactic acidosis. Lactic acidosis is characterised by acidotic dyspnoea, abdominal pain, muscle cramps, asthenia and hypothermia followed by coma. In case of suspected symptoms, the patient should stop taking metformin and seek immediate medical attention. Diagnostic laboratory findings are decreased blood pH (< 7.35), increased plasma lactate levels (> 5 mmol/L) and an increased anion gap and lactate/pyruvate ratio.
Patients with known or suspected mitochondrial diseases:
In patients with known mitochondrial diseases such as Mitochondrial Encephalopathy with Lactic Acidosis, and Stroke-like episodes (MELAS) syndrome and Maternal inherited diabetes and deafness (MIDD), metformin is not recommended due to the risk of lactic acidosis exacerbation and neurologic complications which may lead to worsening of the disease.
In case of signs and symptoms suggestive of MELAS syndrome or MIDD after the intake of metformin, treatment with metformin should be withdrawn immediately and prompt diagnostic evaluation should be performed.
Renal function
GFR should be assessed before treatment initiation and regularly thereafter, see section 4.2.
Metformin is contraindicated in patients with GFR < 30 mL/min and should be temporarily discontinued in the presence of conditions that alter renal function, see section 4.3.
Cardiac function
Patients with heart failure are more at risk of hypoxia and renal insufficiency. In patients with stable chronic heart failure, metformin may be used with a regular monitoring of cardiac and renal function.
For patients with acute and unstable heart failure, metformin is contraindicated (see section 4.3).
Administration of iodinated contrast media
Intravascular administration of iodinated contrast agents may lead to contrast induced nephropathy, resulting in metformin accumulation and an increased risk of lactic acidosis. Metformin should be discontinued prior to or at the time of the imaging procedure and not restarted until at least 48 hours after, provided that renal function has been re-evaluated and found to be stable, see sections 4.2 and 4.5.
Surgery
Metformin must be discontinued at the time of surgery under general, spinal or epidural anaesthesia. Therapy may be restarted no earlier than 48 hours following surgery or resumption of oral nutrition and provided that renal function has been re- evaluated and found to be stable.
Paediatric population
The diagnosis of type 2 diabetes mellitus should be confirmed before treatment with metformin is initiated.
No effect of metformin on growth and puberty has been detected during controlled clinical studies of one-year duration but no long-term data on these specific points are available. Therefore, a careful follow-up of the effect of metformin on these parameters in metformin-treated children, especially prepubescent children, is recommended.
Children aged between 10 and 12 years
Only 15 subjects aged between 10 and 12 years were included in the controlled clinical studies conducted in children and adolescents. Although efficacy and safety of metformin in these children did not differ from efficacy and safety in older children and adolescents, particular caution is recommended when prescribing to children aged between 10 and 12 years.
Other precautions
All patients should continue their diet with a regular distribution of carbohydrate intake during the day. Overweight patients should continue their energy-restricted diet.
The usual laboratory tests for diabetes monitoring should be performed regularly.
Metformin alone does not cause hypoglycaemia, but caution is advised when it is used in combination with insulin or other oral antidiabetics (e.g. sulfonylureas or meglitinides).
Metformin may reduce vitamin B12 serum levels. The risk of low vitamin B12 levels increases with increasing metformin dose, treatment duration, and/or in patients with risk factors known to cause vitamin B12 deficiency. In case of suspicion of vitamin B12 deficiency (such as anaemia or neuropathy), vitamin B12 serum levels should be monitored. Periodic vitamin B12 monitoring could be necessary in patients with risk factors for vitamin B12 deficiency. Metformin therapy should be continued for as long as it is tolerated and not contra-indicated and appropriate corrective treatment for vitamin B12 deficiency provided in line with current clinical guidelines.
Concomitant use not recommended
Alcohol
Alcohol intoxication is associated with an increased risk of lactic acidosis, particularly in case of fasting, malnutrition or hepatic impairment.
Iodinated contrast media
Metformin must be discontinued prior to, or at the time of the imaging procedure and not restarted until at least 48 hours after, provided that renal function has been re-evaluated and found to be stable, see sections 4.2 and 4.4.
Combinations requiring precautions for use
Some medicinal products can adversely affect renal function which may increase the risk of lactic acidosis, e.g. NSAIDs, including selective cyclo- oxygenase (COX) II inhibitors, ACE inhibitors, angiotensin II receptor antagonists and diuretics, especially loop diuretics. When starting or using such products in combination with metformin, close monitoring of renal function is necessary.
Medicinal products with intrinsic hyperglycaemic activity (e.g. glucocorticoids (systemic and local routes) and sympathomimetics)
More frequent blood glucose monitoring may be required, especially at the beginning of treatment. If necessary, adjust the metformin dosage during therapy with the respective medicinal product and upon its discontinuation.
Organic cation transporters (OCT)
Metformin is a substrate of both transporters OCT1 and OCT2. Co-administration of metformin with:
• Inhibitors of OCT1 (such as verapamil) may reduce efficacy of metformin.
• Inducers of OCT1 (such as rifampicin) may increase gastrointestinal absorption and efficacy of metformin.
• Inhibitors of OCT2 (such as cimetidine, dolutegravir, ranolazine, trimethoprime, vandetanib, isavuconazole) may decrease the renal elimination of metformin and thus lead to an increase in metformin plasma concentration.
• Inhibitors of both OCT1 and OCT2 (such as crizotinib, olaparib) may alter efficacy and renal elimination of metformin.
Caution is therefore advised, especially in patients with renal impairment, when these drugs are co-administered with metformin, as metformin plasma concentration may increase. If needed, dose adjustment of metformin may be considered as OCT inhibitors/inducers may alter the efficacy of metformin.
Pregnancy
Uncontrolled hyperglycaemia in the periconceptional phase and during pregnancy (gestational or permanent) is associated with increased risk of congenital abnormalities, pregnancy loss, pregnancy-induced hypertension, preeclampsia, and perinatal mortality. It is important to maintain blood glucose levels as close to normal as possible throughout pregnancy, to reduce the risk of adverse hyperglycaemia- related outcomes to the mother and her child.
Metformin crosses the placenta with levels that can be as high as maternal concentrations.
A large amount of data on pregnant women (more than 1000 exposed outcomes) from a register-based cohort study and published data (meta-analyses, clinical studies, and registries) indicates no increased risk of congenital abnormalities nor feto/neonatal toxicity after exposure to metformin in the periconceptional phase and/or during pregnancy.
There is limited and inconclusive evidence on the metformin effect on the long-term weight outcome of children exposed in utero. Metformin does not appear to affect motor and social development up to 4 years of age in children exposed during pregnancy although data on long term outcomes are limited.
If clinically needed, the use of metformin can be considered during pregnancy and in the periconceptional phase as an addition or an alternative to insulin.
Breast-feeding
Metformin is excreted into human breast milk. No adverse effects were observed in breastfed newborns/infants. However, as only limited data are available, breast- feeding is not recommended during metformin treatment. A decision on whether to discontinue breast-feeding should be made, taking into account the benefit of breast- feeding and the potential risk to adverse effects on the child.
Fertility
Fertility of male or female rats was unaffected by metformin when administered at doses as high as 600 mg/kg/day, which is approximately three times the maximum recommended human daily dose based on body surface area comparisons.
Metformin monotherapy does not cause hypoglycaemia and therefore has no effect on the ability to drive or to use machines.
However, patients should be alerted to the risk of hypoglycaemia when metformin is used in combination with other antidiabetic agents (e.g. sulfonylureas, insulin, or meglitinides).
During treatment initiation, the most common adverse reactions are nausea, vomiting, diarrhoea, abdominal pain and loss of appetite which resolve spontaneously in most cases. To prevent them, it is recommended to take metformin in 2 or 3 daily doses and to increase slowly the doses.
The following adverse reactions may occur under treatment with metformin. Frequencies are defined as follows: very common: (≥ 1/10); common (≥ 1/100 to < 1/10); uncommon (≥ 1/1,000 to < 1/100); rare (≥ 1/10,000 to < 1/1,000); very rare (< 1/10,000), frequency not known (cannot be estimated from the available data).
Within each frequency grouping, adverse reactions are presented in order of decreasing seriousness.
Metabolism and nutrition disorders
Common
• Vitamin B12 decrease/deficiency (see section 4.4).
Very rare
• Lactic acidosis (see section 4.4).
Nervous system disorders
Common
• Taste disturbance
Gastrointestinal disorders
Very common
• Gastrointestinal disorders such as nausea, vomiting, diarrhoea, abdominal pain and loss of appetite. These undesirable effects occur most frequently during initiation of therapy and resolve spontaneously in most cases. To prevent them, it is recommended that metformin be taken in 2 or 3 daily doses during or after meals. A slow increase of the dose may also improve gastrointestinal tolerability.
Hepatobiliary disorders
Very rare
• Isolated reports of liver function tests abnormalities or hepatitis resolving upon metformin discontinuation.
Skin and subcutaneous tissue disorders
Very rare
• Skin reactions such as erythema, pruritus, urticaria
Paediatric population
In published and post marketing data and in controlled clinical studies in a limited paediatric population aged 10 – 16 years treated during 1 year, adverse event reporting was similar in nature and severity to that reported in adults.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.
Hypoglycaemia has not been seen with metformin hydrochloride doses of up to 85 g, although lactic acidosis has occurred in such circumstances. High overdose of metformin or concomitant risks may lead to lactic acidosis. Lactic acidosis is a medical emergency and must be treated in hospital. The most effective method to remove lactate and metformin is haemodialysis.
Ask anything about Metformin 850 mg film-coated tablets. The assistant answers only from this leaflet — if the leaflet does not cover it, it will say so. It does not give medical advice.
Answers come from the patient leaflet published on the electronic medicines compendium (emc). They are not medical advice. Ask a pharmacist or your GP if you are unsure. For urgent help call NHS 111, or 999 in an emergency.
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