Metformin

Pregnancy & gynaecology-specific. Every dose row is source-referenced; verify against institutional protocols.

MetforminBiguanide

Regimens checked: 2026-10-17. Each indication has its own preparation, limits and safety checks.

Metformin: indication-specific regimens
Indication	Dose	Route	Frequency	Duration / preparation	Maximum	Monitoring / cautions
Selected GDM/type 2 diabetes; assess glucose, renal function and suitability for metformin versus insulin MSFchecked	Week 1: 500 mg with breakfast; week 2: 500 mg twice daily; increase by 500 mg/week if tolerated and needed	Oral	Once daily initially, then twice daily with meals	While indicated and tolerated; GDM treatment is normally stopped after birth, with a diabetes follow-up plan · 500 mg tablets taken with meals. Use slower titration for gastrointestinal intolerance; do not silently substitute a modified-release product NICE NG3 permits metformin in selected pregnancies; placental transfer and treatment alternatives should be discussed. Renal / hepatic: Avoid if eGFR <30; reduced dosing/closer review with moderate impairment; withhold during acute dehydration, hypoxia or renal deterioration	2 g/day (1 g twice daily) for this MSF regimen	Monitor Fasting and post-meal glucose; renal function before treatment and with acute illness; B12 with long-term use Escalate to insulin when glucose targets are not reached or metformin is unsuitable Contraindications / cautions DKA, hypoxia, major dehydration or severe renal impairment
Metabolic features of PCOS, particularly adults with BMI ≥25; not an interchangeable GDM regimen International PCOS Guideline Network · 2023checked	Start 500 mg/day with food; increase by 500 mg every 1–2 weeks if tolerated toward the individually required dose	Oral	Once daily initially, then divided with meals; extended-release requires its own product instructions	Continue while metabolic benefit outweighs adverse effects; review the indication when pregnancy occurs · Use 500 mg immediate-release tablets for this example; slow titration reduces GI effects Lifestyle treatment remains foundational. Letrozole is the separate first-line ovulation-induction option.	Suggested PCOS guideline maximum 2.5 g/day in adults and 2 g/day in adolescents, subject to the lower licensed product/renal limit	Monitor Metabolic response, renal function, GI tolerance and B12 if risk factors/long-term therapy Contraindications / cautions eGFR <30, metabolic acidosis, hypoxia or major dehydration; withhold during serious acute illness

Pregnancy safety

NICE permits selected pregnancy use; discuss placental transfer, glucose targets and insulin alternatives.

Lactation

Compatible

Adverse effects

GI upset (titration), B12 deficiency long-term

MSFcheckedIN REVIEW