What is the proper way to take metformin (biguanide oral hypoglycemic)

How to Take Metformin

Metformin should be started at a low dose of 500 mg once or twice daily with meals and gradually increased to minimize gastrointestinal side effects, with a maximum effective dose of up to 2,000-2,550 mg daily in divided doses. 1

Initial Dosing and Titration

• Starting dose:

  • 500 mg orally twice a day with meals, OR
  • 850 mg once a day with a meal 1, 2

• Titration schedule:

  • Increase by 500 mg weekly or 850 mg every 2 weeks
  • Base increases on glycemic control and tolerability 1
  • After 5-7 days, if no gastrointestinal side effects occur, advance to 850 mg or two 500 mg tablets twice daily 2
  • If gastrointestinal side effects appear, decrease to previous lower dose and try to advance the dose later 2

• Maximum daily dose:

  • Up to 2,550 mg per day in divided doses
  • Doses above 2,000 mg may be better tolerated when given three times a day with meals 1
  • Most effective dose is often 850 mg twice daily 2

Administration Tips

• Always take with food (breakfast and/or dinner) to minimize gastrointestinal side effects 2
• For extended-release formulations:
  • Take once daily with the evening meal 3
  • Do not crush or chew extended-release tablets; swallow whole

Special Considerations

Renal Function

• Before starting: Assess renal function 1
• Contraindicated: eGFR below 30 mL/min/1.73 m² 1, 2
• Dose adjustment:
  • eGFR 45-59 mL/min/1.73 m²: Consider dose reduction 2
  • eGFR 30-44 mL/min/1.73 m²: Reduce dose by half of maximum recommended dose 2
  • Monitor kidney function at least every 3-6 months when eGFR is <60 mL/min/1.73 m² 2

Imaging Procedures

• Temporarily discontinue metformin:
  • At the time of or prior to iodinated contrast imaging procedures in patients with eGFR 30-60 mL/min/1.73 m² 1
  • In patients with history of liver disease, alcoholism, or heart failure receiving contrast 1
  • Re-evaluate eGFR 48 hours after imaging; restart if renal function is stable 1

During Illness or Surgery

• Temporarily discontinue during:
  • Acute illness that may compromise renal or liver function
  • Hospitalizations
  • Major surgical procedures 2

Managing Side Effects

• Gastrointestinal side effects (most common):

  • Bloating, abdominal discomfort, diarrhea
  • Usually improve with time on therapy
  • Taking medication with food or 15 minutes after meals helps reduce symptoms 2
  • Consider extended-release formulation if GI intolerance persists with immediate-release 3

• Vitamin B12 deficiency:

  • Long-term use may cause vitamin B12 deficiency 2
  • Periodic measurement of vitamin B12 levels is recommended, especially in patients with anemia or peripheral neuropathy 2

During Fasting Periods

• If taking once daily: Take at main mealtime
• If taking twice daily: Split dose between two meals 2

Common Pitfalls to Avoid

1. Starting with too high a dose - This increases risk of GI side effects and may lead to discontinuation
2. Taking on an empty stomach - Always take with meals to reduce GI side effects
3. Not monitoring renal function - Regular monitoring is essential, especially in older adults
4. Failing to temporarily discontinue during acute illness, surgery, or contrast imaging studies
5. Not checking vitamin B12 levels with long-term use

By following these guidelines, patients can maximize the benefits of metformin while minimizing potential side effects, leading to better medication adherence and glycemic control.