What it does
Metformin is a medication commonly used to manage blood sugar levels in people with diabetes.
Commonly used for: type 2 diabetes mellitus, high blood sugar (hyperglycemia)
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Source: Food and Drugs Authority · fetched 2026-04-18 08:42:00 · updated 2026-10-02 04:00:07
About this medicine
Metformin is a medication commonly used to manage blood sugar levels in people with diabetes.
What it treats
- type 2 diabetes mellitus
- high blood sugar (hyperglycemia)
How it works
Metformin helps lower blood sugar levels by improving how your body responds to insulin and reducing sugar production in the liver.
Who it's for
It is mainly for adults with type 2 diabetes, but may also be used in some children and adolescents.
AI-assisted summary grounded in BNF data - general information only, not medical advice. Always confirm with your pharmacist or doctor.
Clinical monograph: hmetformin
Metformin is an oral antihyperglycemic agent primarily used in the management of type 2 diabetes mellitus. It is a biguanide that improves glycemic control and has additional benefits such as weight neutrality or modest weight loss, and potential cardiovascular benefits.
Indications
- Type 2 diabetes mellitus
- Polycystic ovary syndrome (PCOS)
- Weight management in diabetic patients
Dosage
Children: Refer to the BNF for Children for specific dosing guidelines.
Adults: Refer to the BNF for specific dosing guidelines.
Mechanism of action
Metformin primarily works by decreasing hepatic glucose production, particularly by reducing gluconeogenesis in the liver. It also enhances insulin sensitivity in peripheral tissues, particularly muscle, which leads to improved glucose uptake and utilization. Furthermore, metformin slows intestinal absorption of glucose.
Pharmacodynamics
Metformin does not stimulate insulin secretion from the pancreas, hence it does not cause hypoglycemia when used alone. The drug may also have favorable effects on lipid profiles and may reduce the risk of macrovascular complications related to diabetes.
Pharmacokinetics
Metformin is absorbed from the gastrointestinal tract, with peak plasma concentrations occurring approximately 2 to 3 hours after administration. It has a bioavailability of about 50-60% after oral doses. The drug is not metabolized and is excreted unchanged in the urine. It has a half-life of about 6.2 hours, and its effects can last beyond this due to the gradual release from tissues.
Contra-indications
- Severe renal impairment
- Acute or chronic metabolic acidosis
- Diabetic ketoacidosis
- Hypersensitivity to metformin or any excipients
Adverse effects
- Gastrointestinal disturbances (nausea, vomiting, diarrhea, abdominal pain)
- Lactic acidosis (rare but serious)
- Vitamin B12 deficiency
- Skin reactions (rash, pruritus)
Interactions
- Alcohol (increases risk of lactic acidosis)
- Cationic drugs (may affect renal clearance)
- Iodinated contrast media (risk of lactic acidosis and acute renal failure)
Precautions
- Monitor renal function regularly
- Use with caution in patients with hepatic impairment
- Discontinue prior to surgical procedures or during acute illness
- Ensure adequate hydration to reduce risk of lactic acidosis
Pregnancy
Metformin is not recommended during pregnancy unless the potential benefit justifies the potential risk to the fetus. It is preferred to use insulin for glycemic control.
Breast-feeding
Metformin is excreted in breast milk in small amounts. It is considered safe to use during breastfeeding.
Storage
Store at room temperature, away from moisture and heat. Keep out of reach of children.
Formulations
- Tablets
- Extended-release tablets
- Oral solution
AI-synthesized from BNF references - general information only, not a substitute for professional medical advice or the current BNF. Verify doses with a pharmacist.