Metformin
Metformin is the cheapest prescription weight-loss adjunct — modest results but a strong safety record and near-universal insurance coverage.
- Manufacturer
- Various generic
- Drug class
- Biguanide
- Dose range
- 500 mg → 2,000 mg daily
- Average monthly cost
- $4–$20 generic · often $0 with insurance
- Insurance covered
- Often, with prior authorization
Overview
Metformin is the world's most-prescribed diabetes medication and a common off-label weight-loss adjunct, especially for patients with PCOS, insulin resistance, or prediabetes. Expected weight loss is modest — typically 3–7% of body weight — but it's nearly free, well-tolerated long-term, and pairs safely with GLP-1s for an additive effect.
How it works
Metformin reduces hepatic glucose production and improves insulin sensitivity. The weight-loss effect comes from improved insulin signaling and modest appetite reduction, not direct fat metabolism.
Side effects
- GI upset, especially when starting (use extended-release to reduce)
- Vitamin B12 deficiency with long-term use
- Rare: lactic acidosis (mostly in patients with kidney disease)
- Not appropriate for eGFR < 30
Who should consider Metformin
Adults with prediabetes, PCOS, or insulin resistance who want a low-cost, low-risk starting medication, or who want to pair it with a GLP-1 for additional metabolic benefit.
Telehealth programs that prescribe Metformin
Editorial only — not medical advice. Drug pricing and availability change frequently; verify with the prescribing program before relying on any figure on this page.