Formulary
Metformin hydrochloride: Indications, Dosing, Side Effects and Interactions
Metformin exerts its effect mainly by decreasing gluconeogenesis and by increasing peripheral utilisation of glucose; since it acts only in the presence of...
MedNext Academy | 7 min read
Metformin hydrochloride: Indications, Dosing, Side Effects and Interactions
Metformin exerts its effect mainly by decreasing gluconeogenesis and by increasing peripheral utilisation of glucose; since it acts only in the presence of...
Drug action
Metformin exerts its effect mainly by decreasing gluconeogenesis and by increasing peripheral utilisation of glucose; since it acts only in the presence of endogenous insulin it is effective only if there are some residual functioning pancreatic islet cells.
Indications and dose
**Type 2 diabetes mellitus [monotherapy or in combination with other antidiabetic drugs (including insulin)]**
- **Child** (By Mouth Using Immediate-Release Medicines): 10-17 years (specialist use only) Initially 500 mg once daily; increased if necessary to 2 g daily in 2-3 divided doses, dose to be adjusted according to response at intervals of at least 1 week.
- **Adult** (By Mouth Using Immediate-Release Medicines): Initially 500 mg once daily for at least 1 week, dose to be taken with breakfast, then 500 mg twice daily for at least 1 week, dose to be taken with breakfast and evening meal, then 500 mg 3 times a day, dose to be taken with breakfast, lunch and evening meal, dose can be increased if necessary up to maximum 2 g per day.
- **Adult** (By Mouth Using Modified-Release Medicines): Initially 500 mg once daily, dose to be taken with evening meal, then increased if necessary up to 2 g once daily, dose to be taken with evening meal, dose increased gradually, every 10-15 days; 2 g total daily dose may alternatively be given as 1 g twice daily with meals only if control not achieved with once daily dose regimen. If control still not achieved then change to standard release tablets.
**Type 2 diabetes mellitus [reduction in risk or delay of onset]**
- **Adult** (By Mouth Using Modified-Release Medicines): 18-74 years Initially 500 mg once daily, dose to be taken with evening meal, then increased if necessary up to 2 g once daily, dose to be taken with evening meal, dose increased gradually, every 10-15 days. For further information on risk factors-consult product literature.
**Type 1 diabetes mellitus [in combination with insulin in individuals with a BMI of 25 kg/m2or more (23 kg/m2or more**
- **Adult** (By Mouth Using Immediate-Release Medicines): Type 1 diabetes mellitus [in combination with insulin in individuals with a BMI of 25 kg/m 2 or more (23 kg/m 2 or more for individuals from South Asian and related family backgrounds)] Initially 500 mg once daily for at least 1 week, dose to be taken with breakfast, then 500 mg twice daily for at least 1 week, dose to be taken with breakfast and evening meal, then 500 mg 3 times a day, dose to be taken with breakfast, lunch and evening meal, dose can be increased if necessary up to maximum 2 g per day.
- **Adult** (By Mouth Using Modified-Release Medicines): Initially 500 mg once daily, dose to be taken with evening meal, then increased if necessary up to 2 g daily in 1-2 divided doses, dose to be taken with meal(s), dose increased gradually, every 10-15 days.
**Polycystic ovary syndrome**
- **Adult** (By Mouth Using Immediate-Release Medicines): (initiated by a specialist) Initially 500 mg once daily for 1 week, dose to be taken with breakfast, then 500 mg twice daily for 1 week, dose to be taken with breakfast and evening meal, then 1.5-1.7 g daily in 2-3 divided doses, dose to be taken with meals.
**Type 2 diabetes mellitus [monotherapy or in combination with other antidiabetic drugs (including insulin)] for metformin hydrochloride**
- **Child 8-9 years (specialist use only)** (By mouth using immediate-release medicines): Initially 200-250 mg once daily; increased if necessary up to 2 g daily in 2-3 divided doses, dose to be adjusted according to response at intervals of at least 1 week.
- **Child 10-17 years (specialist use only)** (By mouth using immediate-release medicines): Initially 500 mg once daily; increased if necessary to 2 g daily in 2-3 divided doses, dose to be adjusted according to response at intervals of at least 1 week.
Cautions
General cautions: Risk factors for lactic acidosis Specific cautions: When used for type 1 diabetes mellitus in adults Recurrent lactic acidosis (in adults) Cautions, further information Risk factors for lactic acidosis Manufacturer advises caution in chronic stable heart failure (monitor cardiac function), and concomitant use of drugs that can acutely impair renal function; interrupt treatment if dehydration occurs, and avoid in conditions that can acutely worsen renal function, or cause tissue hypoxia. Elderly In adults: Screening Tool of Older Persons' potentially inappropriate Prescriptions (STOPP) criteria to aid medication reviews (see Prescribing in the elderly for information): potentially inappropriate if eGFR less than 30 mL/minute/1.73 m 2 (contra-indicated in severe renal impairment; risk of lactic acidosis).
Contraindications
Acute metabolic acidosis (including lactic acidosis and diabetic ketoacidosis)
Side effects
Common or very common Abdominal pain; appetite decreased; diarrhoea; gastrointestinal disorder; nausea; taste altered; vitamin B12 deficiency; vomiting Rare or very rare Hepatitis; lactic acidosis (discontinue); skin reactions Side-effects, further information Gastrointestinal side-effects are most frequent during treatment initiation and usually resolve spontaneously. A slow increase in dose may improve tolerability.
Interactions
**Other interactions (20):**
- Coadministration of 100 mg alogliptin once daily and 1 000 mg metformin hydrochloride twice daily for 6 days in healthy subjects had no clinically relevant effects on the pharmacokinetics of...
- Specific pharmacokinetic drug interaction studies have not been performed with Alogliptin/Metformin Hydrochloride.
- The following section outlines the interactions observed with the individual components of Alogliptin/Metformin Hydrochloride as reported in their respective Summary of Product Characteristics.
- Interactions with metformin Concomitant use not recommended Alcohol Alcohol intoxication is associated with an increased risk of lactic acidosis, particularly in case of fasting, malnutrition or...
- Iodinated contrast agents Alogliptin/Metformin Hydrochloride must be discontinued prior to or at the time of the imaging procedure and not restarted until at least 48 hours after, provided that...
- Cationic medicinal products Cationic substances that are eliminated by renal tubular secretion (e.g.
Pregnancy
Important safety information For metformin hydrochloride MHRA/CHM advice: Metformin in pregnancy: study shows no safety concerns (March 2022) European and CHM reviews of data from a large cohort study of Finnish population registries did not identify any safety issues with the use of metformin during pregnancy. Product literature for single-ingredient metformin preparations was subsequently updated to permit its use as an adjunct or alternative to insulin during pregnancy and the periconception period, if clinically indicated. MHRA/CHM advice: Metformin and reduced vitamin B 12 levels: new advice for monitoring patients at risk (June 2022) A European review, with input from the MHRA, has found vitamin B 12 deficiency to be a common side-effect in patients treated with metformin, especially in those receiving a higher dose or longer treatment duration and in those with risk factors for vitamin B 12 deficiency. Healthcare professionals are advised to check serum-vitamin B 12 levels if deficiency is suspected and consider periodic monitoring in patients with risk factors for deficiency. Vitamin B 12 deficiency should be treated according to current guidelines and treatment with metformin continued for as long as it is tolerated. Patients and their carers should be counselled on the signs and symptoms of vitamin B 12 deficiency and advised to seek medical advice if these occur. Patients should continue taking metformin unless they are advised to stop.
Breast feeding
May be used during breast-feeding in women with pre-existing diabetes. A
Hepatic impairment
Withdraw if tissue hypoxia likely.
Renal impairment
See Prescribing in renal impairment . In adults: Manufacturer advises avoid if eGFR is less than 30 mL/minute/1.73 m 2 . In children: Manufacturer advises avoid if estimated glomerular filtration rate is less than 30 mL/minute/1.73 m 2 . Dose adjustments In children: Manufacturer advises consider dose reduction in moderate impairment. In adults: Manufacturer advises reduce dose in moderate impairment-consult product literature.
Medicinal forms
Capsule,Tablet,Tablet,Solution,Solution
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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