Metformin

What Is Metformin?

Metformin is one of the most established oral medicines for type 2 diabetes. It improves the way the body responds to insulin and reduces excess glucose production by the liver. Metformin is not insulin. It does not usually cause low blood sugar when used alone and does not normally cause weight gain. It can be prescribed by itself or with other diabetes medicines.

Metformin Uses

The main approved use of metformin is improving blood glucose control in eligible adults and children with type 2 diabetes. Age approval depends on the formulation and country. Metformin is also used outside its main licensed indication in selected people with polycystic ovary syndrome. It can improve insulin resistance and support ovulation in some patients with PCOS. It should not be described as a direct fertility medicine or a treatment suitable for everyone with irregular periods. Metformin is not used to treat type 1 diabetes or diabetic ketoacidosis.

How Does Metformin Work?

Metformin reduces the amount of glucose released by the liver. It improves insulin sensitivity so muscle and other tissues can use glucose more effectively. It also has effects on glucose absorption and metabolism in the digestive system. Unlike sulfonylureas, metformin does not directly force the pancreas to release more insulin. This explains its low risk of hypoglycaemia when used alone.

Metformin Dosage Information

Metformin dosage depends on the formulation, age, kidney function, blood glucose and digestive tolerance. Treatment usually starts with a low dose taken with food. The dose is then increased gradually.

An immediate release regimen can begin with metformin 500 mg once or twice daily with meals. Extended release metformin commonly begins at 500 mg once daily with the evening meal. Maximum doses differ between formulations and products. These are label-based examples and not personal dosing instructions. Never copy another person’s dose or increase the amount to speed up results.

Metformin 500 mg, 850 mg and 1000 mg

Common tablet strengths include:

• Metformin 500 mg

• Metformin 850 mg

• Metformin 1000 mg

The number on the pack shows the amount of metformin in each tablet. It does not show how many tablets a person should take. Immediate release and extended release tablets with the same strength have different release patterns.

Metformin Immediate Release vs Extended Release

Immediate release metformin releases the medicine more quickly and can be taken more than once daily. Extended release metformin releases it slowly and is commonly taken once daily. Extended release tablets can cause fewer digestive problems for some patients. They must be swallowed whole. Do not crush, cut or chew them unless the specific product instructions allow it.

Metformin Side Effects

Common metformin side effects include:

• Nausea

• Diarrhoea

• Stomach pain

• Gas

• Reduced appetite

• Vomiting

• Metallic or altered taste

Taking metformin with food and increasing the dose gradually can improve tolerance. Persistent diarrhoea or vomiting needs medical advice.

Metformin and Vitamin B12

Long-term metformin treatment can reduce vitamin B12 absorption. Deficiency can cause tiredness, mouth ulcers, a sore tongue, pale skin, pins and needles, balance problems or worsening nerve symptoms.

Vitamin B12 testing is considered when symptoms appear or when a person has risk factors for deficiency. Do not stop metformin only because B12 is low. A healthcare professional can treat the deficiency and review ongoing therapy.

Lactic Acidosis Warning

Metformin can rarely cause lactic acidosis. This is a medical emergency caused by excess lactic acid in the blood.

Seek urgent care for severe weakness, muscle pain, unusual sleepiness, stomach discomfort, vomiting, slow or difficult breathing, dizziness or feeling very cold.

Risk increases with severe kidney impairment, dehydration, serious infection, low oxygen conditions, liver disease, heavy alcohol intake and some procedures.

Kidney Safety

Metformin is removed from the body by the kidneys. Kidney function must be assessed before treatment and checked when clinically needed.

Metformin is contraindicated in severe kidney impairment. Dose or treatment decisions at other kidney levels depend on the estimated glomerular filtration rate and current product guidance.

Warnings and Drug Interactions

Tell the healthcare professional about every medicine and supplement. Important points include:

• Insulin and sulfonylureas can increase low blood sugar risk

• Iodinated contrast used for some scans can require a temporary pause

• Carbonic anhydrase inhibitors can increase acidosis risk

• Medicines that affect kidney function need review

• Heavy alcohol use increases lactic acidosis risk

Vomiting, diarrhoea, fever or reduced fluid intake can require sick day instructions.

Who Should Avoid Metformin?

Metformin is unsuitable for people with:

• A serious allergy to metformin

• Severe kidney impairment

• Acute or chronic metabolic acidosis

• Diabetic ketoacidosis

Specialist review is needed during severe illness, dehydration, liver disease, heavy alcohol use, pregnancy, surgery or before certain contrast scans.

Storage Instructions

Keep metformin in its original packaging at the temperature shown on the label. Protect it from moisture and excess heat. Keep it away from children and anyone for whom it was not supplied.