metformin

Adjunctive therapy • Brands: Glucophage, Glucophage XR, Fortamet, Glumetza

Last reviewed: 2025-12-30

General information

Primary label indications include: Type 2 diabetes mellitus; adjunct to diet and exercise for glycemic control (label).
Class: Adjunctive therapy
Common US brands: Glucophage, Glucophage XR, Fortamet, Glumetza
Typical dose range: Label initiation commonly starts at 500 mg once or twice daily with meals, then increases in weekly steps as tolerated; total daily maximum varies by formulation/manufacturer (label).
Therapeutic drug monitoring not routinely recommended.
Last reviewed: 2025-12-30

Dosing & forms

Forms/strengths: Immediate-release tablets: 500 mg, 850 mg, 1000 mg; oral solution exists (label/manufacturer-dependent).; Extended-release tablets exist in multiple strengths; products differ and are not always interchangeable without confirming release profile and dose equivalence (label/clinical).
Frequency: Label initiation commonly starts at 500 mg once or twice daily with meals, then increases in weekly steps as tolerated; total daily maximum varies by formulation/manufacturer (label).
Food: Take with food.
Typical range: Label initiation commonly starts at 500 mg once or twice daily with meals, then increases in weekly steps as tolerated; total daily maximum varies by formulation/manufacturer (label).

Mechanism (brief)

Biguanide antihyperglycemic that reduces hepatic glucose production and improves insulin sensitivity; does not typically cause hypoglycemia as monotherapy. In psychiatry it is commonly used off label to help mitigate antipsychotic-associated weight gain and metabolic risk.

Metabolism & Half‑life

Metabolism: Not metabolized; eliminated by renal filtration and active tubular secretion (label).
Half‑life: Single-dose mean 6.2 h

Therapeutic Drug Monitoring (TDM)

Recommended: No

View labelExact

Monitoring highlights

Baseline and periodic renal function (eGFR/creatinine) to guide dosing and continuation (label).
Metabolic monitoring (weight, waist circumference, fasting glucose/A1c, lipids) integrated with antipsychotic monitoring workflows (clinical).
Vitamin B12 level assessment when symptoms or prolonged treatment suggests deficiency (label/clinical).
Review for high-risk contexts for lactic acidosis (dehydration, sepsis, hypoxemia, heavy alcohol use) and pause therapy during acute illness when risk rises (label/clinical).

Sources

Metformin hydrochloride tablets prescribing information — DailyMed (2025)
Lifestyle Intervention and Metformin for Treatment of Antipsychotic-Induced Weight Gain — JAMA (2008)
A systematic review of metformin to limit weight gain with atypical antipsychotics — Journal of Clinical Pharmacy and Therapeutics (2011)
Efficacy of Metformin and Topiramate in Prevention and Treatment of Second-Generation Antipsychotic–Induced Weight Gain — The Annals of Pharmacotherapy (2010)
AGNP Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology — Pharmacopsychiatry (2018)

General information

Primary label indications include: Type 2 diabetes mellitus; adjunct to diet and exercise for glycemic control (label).

Class: Adjunctive therapy

Common US brands: Glucophage, Glucophage XR, Fortamet, Glumetza

Typical dose range: Label initiation commonly starts at 500 mg once or twice daily with meals, then increases in weekly steps as tolerated; total daily maximum varies by formulation/manufacturer (label).

Therapeutic drug monitoring not routinely recommended.

Last reviewed: 2025-12-30

Dosing & forms

Forms/strengths: Immediate-release tablets: 500 mg, 850 mg, 1000 mg; oral solution exists (label/manufacturer-dependent).; Extended-release tablets exist in multiple strengths; products differ and are not always interchangeable without confirming release profile and dose equivalence (label/clinical).

Frequency: Label initiation commonly starts at 500 mg once or twice daily with meals, then increases in weekly steps as tolerated; total daily maximum varies by formulation/manufacturer (label).

Food: Take with food.

Typical range: Label initiation commonly starts at 500 mg once or twice daily with meals, then increases in weekly steps as tolerated; total daily maximum varies by formulation/manufacturer (label).

Monitoring highlights

Baseline and periodic renal function (eGFR/creatinine) to guide dosing and continuation (label).

Metabolic monitoring (weight, waist circumference, fasting glucose/A1c, lipids) integrated with antipsychotic monitoring workflows (clinical).

Vitamin B12 level assessment when symptoms or prolonged treatment suggests deficiency (label/clinical).

Review for high-risk contexts for lactic acidosis (dehydration, sepsis, hypoxemia, heavy alcohol use) and pause therapy during acute illness when risk rises (label/clinical).