What it does
Metformin is a medication primarily used to manage blood sugar levels in people with diabetes.
Commonly used for: type 2 diabetes (non-insulin dependent diabetes), polycystic ovary syndrome (PCOS)
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Source: Pharmacy and Poisons Board · fetched 2026-01-28 21:31:08 · updated 2026-07-20 11:05:18
About this medicine
Metformin is a medication primarily used to manage blood sugar levels in people with diabetes.
What it treats
- type 2 diabetes (non-insulin dependent diabetes)
- polycystic ovary syndrome (PCOS)
How it works
Metformin helps lower blood sugar levels by improving how your body responds to insulin and decreasing the amount of sugar your liver produces.
Who it's for
It is suitable for adults and some children with type 2 diabetes.
Cautions
- • Consult your doctor if you have kidney problems or are at risk for kidney issues.
- • Avoid excessive alcohol consumption while taking this medication.
AI-assisted summary grounded in BNF data - general information only, not medical advice. Always confirm with your pharmacist or doctor.
Clinical monograph: metformin500
Metformin is an oral antihyperglycemic agent used primarily in the management of type 2 diabetes mellitus. It belongs to the biguanide class of medications and works by improving insulin sensitivity, decreasing hepatic glucose production, and enhancing peripheral glucose uptake and utilization. Metformin is often used as first-line therapy for type 2 diabetes, especially in overweight patients, and can also be used in polycystic ovary syndrome (PCOS) to manage insulin resistance.
Indications
- Type 2 diabetes mellitus
- Polycystic ovary syndrome (PCOS)
- Prevention of type 2 diabetes in high-risk 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 reduces hepatic glucose production by inhibiting gluconeogenesis and glycogenolysis. It also enhances insulin sensitivity in peripheral tissues, particularly in muscle and adipose tissue, leading to increased glucose uptake. Additionally, metformin may improve lipid profiles and has been associated with weight stabilization or weight loss in some patients.
Pharmacodynamics
Metformin reduces blood glucose levels without causing significant hypoglycemia. Its effects on insulin secretion are minimal, which makes it distinct from other antidiabetic medications. The drug also has favorable effects on lipid metabolism, potentially lowering triglycerides and LDL cholesterol levels.
Pharmacokinetics
Metformin is rapidly absorbed from the gastrointestinal tract, with peak plasma concentrations occurring within 2 to 3 hours after oral administration. It is not metabolized by the liver and is excreted unchanged in the urine. The elimination half-life is approximately 6 hours. Renal function is crucial for the clearance of metformin; thus, dosage adjustments are necessary in patients with impaired renal function to avoid accumulation and potential lactic acidosis.
Contra-indications
- Severe renal impairment (eGFR < 30 mL/min)
- Acute or chronic metabolic acidosis, including diabetic ketoacidosis
- Hypersensitivity to metformin or any of its components
Adverse effects
- Gastrointestinal disturbances (nausea, vomiting, diarrhea)
- Lactic acidosis
- Vitamin B12 deficiency
- Hypoglycemia (when used with other antidiabetic agents)
Interactions
- Cationic drugs that are eliminated by renal tubular secretion may increase the risk of metformin accumulation
- Alcohol can potentiate the effects of metformin on lactate metabolism
- Certain medications (such as diuretics, corticosteroids, and thyroid products) may affect blood glucose levels, necessitating dose adjustments
Precautions
- Monitor renal function regularly, especially in elderly patients
- Caution in patients with hepatic impairment
- Discontinue prior to any imaging studies involving iodinated contrast media and do not restart for at least 48 hours after the procedure if renal function is impaired
Pregnancy
Metformin is considered safe for use during pregnancy if the benefits outweigh the risks, particularly for women with gestational diabetes.
Breast-feeding
Metformin is excreted in breast milk, but it is generally considered safe for breastfeeding mothers, with no adverse effects observed in nursing infants.
Storage
Store in a cool, dry place away from direct light. Keep out of reach of children.
Formulations
- 500 mg immediate-release tablet
- 850 mg immediate-release tablet
- 1000 mg immediate-release tablet
- Extended-release formulations (various strengths)
AI-synthesized from BNF references - general information only, not a substitute for professional medical advice or the current BNF. Verify doses with a pharmacist.