Disclaimer: This article is written for educational purposes only. It does not replace professional medical advice. Always consult a qualified doctor before starting, stopping, or changing any medication.
Metformin is an oral antidiabetic medication widely prescribed as a first-line treatment for type 2 diabetes mellitus. It improves insulin sensitivity, reduces hepatic glucose production, and helps control blood sugar without causing significant hypoglycemia.
What Is Metformin?
Metformin belongs to the biguanide class of antidiabetic drugs. It is recommended globally by clinical guidelines, including the British National Formulary (BNF), due to its proven efficacy, safety profile, and cardiovascular benefits.
- Drug class: Biguanide
- Primary use: Type 2 Diabetes Mellitus
- Additional benefits: Weight neutrality, improved insulin resistance
Mechanism of Action (How Metformin Works)
Metformin lowers blood glucose through multiple mechanisms:
- Decreases glucose production in the liver
- Improves peripheral insulin sensitivity
- Reduces intestinal glucose absorption
Unlike sulfonylureas, metformin does not stimulate insulin secretion, which explains its low risk of hypoglycemia.
Metformin Dosage (BNF-Based Guidance)
Typical adult dosing:
- Starting dose: 500 mg once or twice daily with meals
- Titration: Increase gradually every 1–2 weeks
- Maximum dose: 2000–2550 mg/day (divided doses)
Renal impairment:
- eGFR ≥ 45 ml/min: Safe with monitoring
- eGFR 30–44 ml/min: Dose reduction required
- eGFR < 30 ml/min: Contraindicated
Uses of Metformin
- Type 2 diabetes mellitus
- Prediabetes (in selected cases)
- Polycystic ovary syndrome (PCOS)
- Insulin resistance states
Side Effects of Metformin
Common side effects:
- Nausea
- Diarrhea
- Abdominal discomfort
- Metallic taste
Serious but rare complication:
- Lactic acidosis – usually associated with renal failure, liver disease, or severe dehydration
Drug Interactions (Trending Topic)
Metformin may interact with several commonly used medications:
- Contrast agents (temporary discontinuation required)
- Alcohol (increased lactic acidosis risk)
- Sulfonylureas (risk of hypoglycemia)
Read more about drug safety and interactions:
Metformin vs Sulfonylureas
| Feature | Metformin | Sulfonylureas |
|---|---|---|
| Hypoglycemia risk | Low | High |
| Weight effect | Neutral / Weight loss | Weight gain |
| First-line therapy | Yes | No |
Important Precautions
- Stop metformin temporarily before contrast imaging procedures
- Avoid excessive alcohol intake
- Monitor kidney function regularly
Frequently Asked Questions (FAQs)
Is metformin safe for long-term use?
Yes, metformin is considered safe for long-term use when kidney function is regularly monitored.
Can metformin cause kidney damage?
Metformin does not damage kidneys but should be avoided in severe renal impairment.
Why is metformin stopped before CT scan?
Because contrast agents can temporarily impair kidney function, increasing the risk of lactic acidosis.
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