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A plain-language summary of the cited sources below. Informational only — not medical advice.
Metformin is a medication used to manage type 2 diabetes. It works by lowering blood sugar levels, both when someone hasn't eaten for a while and after meals. Doctors typically prescribe it for adults whose blood sugar isn't adequately controlled through diet and exercise alone, especially when the person is overweight. The body clears metformin fairly quickly—after taking a dose, about half of it leaves the system in roughly six and a half hours.
The most common side effects affect the stomach and digestive system. Your family member might experience nausea, vomiting, diarrhoea, stomach pain, or loss of appetite. Some people notice a change in how things taste. Long-term use can lead to vitamin B12 deficiency, which is why regular monitoring is important.
There is a serious but uncommon side effect called lactic acidosis, where acid builds up in the blood. While rare, it requires immediate medical attention. There have also been isolated reports of liver function test abnormalities or hepatitis that resolved when metformin was stopped.
Metformin isn't suitable for everyone. It shouldn't be used by people with kidney problems, certain metabolic conditions including diabetic ketoacidosis, severe liver disease, heart failure, respiratory failure, or recent heart attack. It's also not appropriate during severe infections, dehydration, shock, significant blood loss, or when someone is acutely unwell in ways that affect kidney function or oxygen delivery to tissues. People scheduled for major surgery or certain medical imaging procedures involving contrast agents may need to temporarily stop taking it.
For prescribing by certain health practitioners Clinical criteria: Treatment criteria: Must be treated by a health practitioner who is any of: (i) a medical practitioner, (ii) a nurse practitioner, (iii) an endorsed midwife who is each of: (a) sharing patient care with a medical practitioner for the current pregnancy episode, (b) continuing existing treatment with this drug that was initiated by a medical practitioner.
“Metformin is a biguanide with anti-hyperglycaemic effects, lowering both basal and postprandial plasma glucose.”
“Following an oral dose, the apparent terminal elimination half-life is approximately 6.5 hours.”
A plain-language summary of the cited sources below. Informational only — not medical advice.
Metformin is a biguanide with anti-hyperglycaemic effects, lowering both basal and postprandial plasma glucose. It is indicated for the treatment of type 2 diabetes mellitus in adults, particularly in overweight patients, when dietary management and exercise alone do not achieve adequate glycaemic control. The apparent terminal elimination half-life following oral administration is approximately 6.5 hours.
Gastrointestinal adverse effects—nausea, vomiting, diarrhoea, abdominal pain, and loss of appetite—are common, along with taste disturbance and vitamin B12 deficiency with prolonged use. Lactic acidosis is a serious adverse effect, and isolated reports of liver function test abnormalities or hepatitis resolving upon metformin discontinuation have been documented. Contraindications include hypersensitivity to metformin, any type of metabolic acidosis, diabetic pre-coma, renal dysfunction (creatinine clearance <60 mL/min), acute conditions that may alter renal function (dehydration, severe infection, shock, intravascular iodinated contrast administration), acute or chronic disease causing tissue hypoxia (cardiac failure, recent myocardial infarction, respiratory failure, pulmonary embolism, acute significant blood loss, sepsis, gangrene, pancreatitis), major surgery, severe hepatic insufficiency, acute alcohol intoxication, alcoholism, and lactation.
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Curated subset. The full adverse-effect list is in the TGA Product Information; click any citation above to open it.