Metformin – most common tablet for type 2 diabetes

Metformin – most common tablet for type 2 diabetes

This is a guide to the world’s most prescribed diabetes medication.

Metformin (brand names include Glucophage and Bolamyn) is the most common first-line medication used to treat Type 2 diabetes. It belongs to a class of medicines called biguanides.

Unlike some treatments that force the body to produce more insulin, metformin works by improving how your body responds to the insulin you already have and reducing the amount of sugar your liver produces.

What is Metformin?

• The Gold Standard: It is the primary medication recommended by the NICE Guidelines (UK) due to its proven safety record and effectiveness.

• An Insulin Sensitiser: It does not “squeeze” the pancreas; instead, it makes your cells more sensitive to insulin.

• Foundation Therapy: It can be used alone or as a base treatment alongside other medications like gliclazide or SGLT2 inhibitors.

How It Works

1. Liver Regulation: It tells your liver to slow down the production of stored glucose.

2. Muscle Absorption: It helps your muscles take up and use glucose from the blood more efficiently.

3. Intestinal Slowing: It slightly slows the absorption of sugar from the food you eat.

Uses – What is Metformin used for?

• Type 2 Diabetes: The primary treatment when lifestyle changes alone are insufficient.

• Prediabetes: Used to prevent the onset of diabetes in high-risk individuals, as noted in the ADA Standards of Care (US).

• PCOS: Often prescribed “off-label” to manage insulin resistance in Polycystic Ovary Syndrome.

Note: Metformin is not used for Type 1 diabetes, where the body produces no insulin at all.

Dose

According to the British National Formulary (BNF), treatment should be initiated at a low dose to minimize gastrointestinal side effects.

• Typical Dose: Starts at 500mg once daily, gradually increasing to a usual dose of 1g to 2g daily.

• Form: Available as Standard Release (immediate) or Sustained/Modified Release (SR/MR). SR versions are often better for those with sensitive stomachs.

• Schedule: Standard tablets are taken 2–3 times a day; SR tablets are usually taken once daily with the evening meal.

Critical Safety Notes:

1. Meals: Always take metformin with or immediately after food to reduce stomach upset.

2. Kidney Function: Metformin should be stopped if the estimated glomerular filtration rate (eGFR) falls below 30 mL/min to avoid the risk of lactic acidosis. And the dose should be reduced at 45 ml/min.

Side Effects

Common Side Effects

• Digestive Issues: Nausea, vomiting, and diarrhoea are common when first starting.

• Metallic Taste: A temporary change in taste perception.

• B12 Deficiency: Long-term use can lower Vitamin B12 levels. The Endocrine Society (US) recommends monitoring for this deficiency periodically.

Rare but Serious

• Lactic Acidosis: A very rare buildup of lactic acid, typically occurring only in patients with severe kidney or liver failure.

Monitoring

Your doctor will monitor several key metrics to ensure the medication is working safely:

• HbA1c Levels: Routine blood tests to track long-term sugar control.

• Kidney Function (eGFR): Checked at least once a year.

• Vitamin B12: Periodic checks, especially if you experience unusual fatigue or numbness.

Comparison: Metformin vs. Gliclazide

Other resources

United Kingdom (UK)

• NICE Guideline [NG28]: Type 2 diabetes in adults: management

• British National Formulary (BNF): Metformin Hydrochloride

United States (US)

• ADA Standards of Care in Diabetes—2026

• Endocrine Society Clinical Practice Guidelines