Metformin

• Gestational diabetes (when diet/exercise fail)
• Type 2 DM in pregnancy
• PCOS-related anovulation / fertility

Activates AMPK → ↓ hepatic gluconeogenesis, ↑ peripheral insulin sensitivity. Does not cause hypoglycaemia alone.

• GI upset most common SE
• Lactic acidosis (rare, renal)
• Acidosis: hold if eGFR <30
• Combine with insulin if targets not met

Start

500 mg OD with food

Titrate

↑ weekly to 500–1000 mg BD–TDS

Max

2,500–3,000 mg/day divided

• AbsoluteeGFR <30 mL/min
• AbsoluteAcute metabolic acidosis, severe sepsis
• CautionPause around iodinated contrast & surgery

• Nausea, diarrhoea, abdominal pain
• Metallic taste
• Vit B12 deficiency (long-term)
• Lactic acidosis (rare)

• • Crosses placenta — no teratogenicity signal.
• • Long-term follow-up of offspring reassuring (MiG-TOFU).
• • Safe in breastfeeding.

• Iodinated contrast

  Caution

  ↑ lactic acidosis risk — hold 48 h

• Insulin

  OK

  Synergistic — common combination

• Alcohol

  Caution

  ↑ lactic acidosis

• 💡 Start before insulin in GDM unless severe hyperglycaemia.
• 💡 Continue intrapartum; review postpartum at 6 weeks with OGTT.