Metformin Refills for 6 Months at Twice Daily Dosing
For a patient taking metformin 1000mg twice daily (2000mg total daily dose) for 6 months, you need 5 refills on a standard 30-day prescription, which provides 60 tablets per month (360 tablets total for 6 months). 1, 2
Prescription Calculation
- A twice-daily regimen requires 60 tablets per 30-day supply (2 tablets × 30 days) 1
- For 6 months of continuous therapy, the total requirement is 360 tablets 2
- Write the initial prescription for a 30-day supply (60 tablets) with 5 refills to cover the full 6-month period 1, 2
Critical Monitoring Requirements Before Each Refill
- Check eGFR at least annually if ≥60 mL/min/1.73 m², or every 3-6 months if <60 mL/min/1.73 m² 1, 3
- The 1000mg twice daily dose (2000mg total) is only appropriate for patients with eGFR ≥60 mL/min/1.73 m² 2, 3
- Reduce to 1000mg total daily dose (500mg twice daily or 1000mg once daily) if eGFR falls to 30-44 mL/min/1.73 m² 1, 2
- Discontinue metformin entirely if eGFR drops below 30 mL/min/1.73 m² 1, 3
Common Pitfalls to Avoid
- Do not continue refilling at 1000mg twice daily without verifying renal function remains adequate (eGFR ≥60 mL/min/1.73 m²) 1, 2
- Hold metformin temporarily before procedures using iodinated contrast if eGFR <60 mL/min/1.73 m², during hospitalizations, or when acute illness may compromise renal function 2, 3
- Monitor for vitamin B12 deficiency in patients treated for more than 4 years, especially those with anemia or peripheral neuropathy 2, 3