Metformin hydrochloride is an oral antihyperglycemic agent belonging to the biguanide class, widely recognized as the first-line pharmacological intervention for the management of type 2 diabetes mellitus. It functions primarily by decreasing hepatic glucose production, reducing intestinal glucose absorption, and improving insulin sensitivity by increasing peripheral glucose uptake and utilization. Its well-established efficacy, favorable safety profile, and low cost have solidified its position as a cornerstone therapy in global diabetes treatment guidelines. This medication is typically prescribed as part of a comprehensive treatment plan that includes dietary modifications, regular physical activity, and, when necessary, other antihyperglycemic agents.

Features

• Active Ingredient: Metformin hydrochloride
• Available Formulations: Immediate-release tablets, extended-release tablets, and oral solution
• Mechanism of Action: Primarily inhibits hepatic gluconeogenesis and enhances peripheral insulin sensitivity
• Prescription Status: Available by prescription only
• Dosing Flexibility: Available in multiple strengths (e.g., 500 mg, 850 mg, 1000 mg)
• Onset of Action: Peak plasma concentration occurs within 1–3 hours for immediate-release formulations

Benefits

• Significantly lowers both fasting and postprandial blood glucose levels
• Promotes modest weight loss or weight neutrality, unlike many other antidiabetic agents
• Reduces hemoglobin A1c (HbA1c) by approximately 1–2%
• Lowers the risk of cardiovascular events in patients with type 2 diabetes
• Does not cause hypoglycemia when used as monotherapy
• May improve lipid profiles by reducing triglycerides and LDL cholesterol

Common use

Metformin is indicated as an adjunct to diet and exercise to improve glycemic control in adults and pediatric patients 10 years of age and older with type 2 diabetes mellitus. It may be used as monotherapy or in combination with other oral antihyperglycemic agents or insulin. Off-label uses include polycystic ovary syndrome (PCOS), prediabetes management, and gestational diabetes in certain clinical scenarios, though these applications require careful medical supervision.

Dosage and direction

The usual starting dose for adults is 500 mg twice daily or 850 mg once daily with meals. Dosage should be titrated gradually to minimize gastrointestinal adverse effects, with increases typically made at weekly intervals. The maximum recommended daily dose is 2550 mg administered in divided doses for immediate-release formulations and 2000 mg once daily for extended-release formulations. For pediatric patients (10–16 years), the starting dose is 500 mg twice daily, with a maximum daily dose of 2000 mg. Extended-release tablets should be swallowed whole and not crushed or chewed, typically administered once daily with the evening meal.

Precautions

• Renal function should be assessed before initiation and regularly during treatment (eGFR should be ≥30 mL/min/1.73m²)
• Temporary discontinuation is recommended for procedures involving intravascular iodinated contrast materials due to risk of contrast-induced nephropathy
• Avoid use in conditions predisposing to renal impairment or hypoxia (e.g., dehydration, severe infection, acute congestive heart failure)
• Monitor vitamin B12 levels annually or as clinically indicated, as long-term use may decrease absorption
• Use with caution in elderly patients and those with hepatic impairment
• Educate patients about the symptoms of lactic acidosis, though this adverse effect is rare

Contraindications

• Severe renal impairment (eGFR below 30 mL/min/1.73m²)
• Acute or chronic metabolic acidosis, including diabetic ketoacidosis
• History of hypersensitivity to metformin or any component of the formulation
• Acute congestive heart failure requiring pharmacological treatment
• Acute myocardial infarction, septicemia, or other conditions associated with hypoperfusion and hypoxia

Possible side effect

Common side effects (≥1%) include:

• Gastrointestinal disturbances: diarrhea, nausea, vomiting, abdominal discomfort, flatulence
• Metallic taste
• Decreased appetite

Less common side effects:

• Lactic acidosis (rare but serious; incidence approximately 0.03 cases per 1000 patient-years)
• Vitamin B12 deficiency with long-term use
• Skin reactions such as rash or urticaria
• Asthenia

Drug interaction

• Cationic drugs: Cimetidine, ranitidine, and other cationic medications may increase metformin exposure by competing for renal tubular secretion
• Alcohol: Excessive alcohol intake increases risk of lactic acidosis and hypoglycemia
• Iodinated contrast materials: Increase risk of acute renal failure and lactic acidosis
• Other hypoglycemic agents: May potentiate glucose-lowering effects when used in combination
• Carbon anhydrase inhibitors: Topiramate or other carbonic anhydrase inhibitors may increase risk of metabolic acidosis

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is almost time for the next scheduled dose. In that case, skip the missed dose and resume the regular dosing schedule. Do not double the dose to make up for a missed one.

Overdose

Metformin overdose, particularly in the presence of contraindications, may lead to lactic acidosis, which is a medical emergency characterized by elevated blood lactate levels, metabolic acidosis, hypothermia, hypotension, and resistant bradyarrhythmias. Hypoglycemia has been reported but is uncommon with metformin monotherapy. Treatment is primarily supportive and should include immediate hemodialysis to correct acidosis and remove metformin.

Storage

Store at controlled room temperature (20–25°C or 68–77°F), with excursions permitted between 15–30°C (59–86°F). Keep container tightly closed and protect from moisture. Keep out of reach of children and pets. Do not use after the expiration date printed on the packaging.

Disclaimer

This information is provided for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional before starting, changing, or stopping any medication. The prescribing physician should be consulted regarding specific medical conditions or treatments. Individual responses to medication may vary.

Reviews

“Metformin has been the foundation of my type 2 diabetes management for over eight years. Its consistent efficacy in controlling my blood glucose levels, combined with minimal side effects after the initial adjustment period, has made it an indispensable part of my treatment regimen.” - Endocrine Specialist, 15 years clinical experience

“While gastrointestinal side effects can be challenging during initiation, slow titration and administration with food significantly improve tolerability. The cardiovascular benefits and weight-neutral profile make it an excellent first-choice medication for most type 2 diabetes patients.” - Clinical Pharmacologist, Diabetes Center

“Extensive clinical trial data and real-world evidence continue to support metformin’s role as first-line therapy. Its mechanism of action addresses fundamental pathophysiological defects in type 2 diabetes, and its long-term safety profile is well-documented across diverse patient populations.” - Research Diabetologist