Introduction
Metformin is the most commonly prescribed medication for type 2 diabetes and has been a first-line treatment for decades, backed by extensive safety data.
What Is Metformin?
Metformin is a biguanide that reduces hepatic glucose production, increases insulin sensitivity, and modestly reduces intestinal glucose absorption without causing hypoglycemia.
How Metformin Works
The drug primarily works by activating AMPK, an enzyme that regulates energy metabolism, leading to decreased glucose output from the liver.
Who Should Take Metformin?
First-line therapy for most type 2 diabetes patients without severe renal impairment (eGFR < 30). Also used for prediabetes and PCOS.
Dosage Guidelines
Starting dose is typically 500 mg twice daily with meals, titrated up to 2,000–2,550 mg daily. Extended-release formulations reduce GI side effects.
Side Effects
GI symptoms (nausea, diarrhea) are most common at initiation. Lactic acidosis is a rare but serious risk, particularly with renal impairment or contrast dye use.
Vitamin B12 Monitoring
Long-term metformin use reduces vitamin B12 absorption. Annual B12 level monitoring is recommended, and supplementation may be necessary.
Drug Interactions
Hold metformin 48 hours before and after iodinated contrast procedures. Avoid in patients with eGFR < 30 mL/min/1.73m².
Metformin and Weight
Unlike many diabetes medications, metformin is weight-neutral to modestly weight-reducing, making it especially valuable for overweight patients with type 2 diabetes.
Conclusion
Metformin remains the cornerstone of type 2 diabetes treatment due to its efficacy, safety profile, low cost, and decades of clinical data supporting its use.