How to write a prescription for metformin 500mg PO daily?

How to Write a Prescription for Metformin 500mg PO Daily

The recommended starting dose for metformin is 500 mg orally once daily, given with meals, which can be gradually titrated based on glycemic control and tolerability. 1

Prescription Writing Format

• Write patient's full name, date of birth, and date of prescription at the top of the prescription 1
• Under medication information, write:
  • Metformin 500 mg tablets 1
  • Sig: Take 1 tablet by mouth once daily with a meal 1, 2
  • Dispense: #30 (thirty) tablets 1
  • Refills: 2-3 (depending on follow-up schedule) 2

Dosing Considerations

• Starting with 500 mg daily improves gastrointestinal tolerability 3, 4
• The medication should be taken with meals to further reduce GI side effects 1, 2
• Extended-release formulation is an alternative option that may improve tolerability and can be given once daily, typically with the evening meal 4, 5
• If prescribing extended-release metformin, specify "Metformin ER 500 mg tablets" on the prescription 5, 6

Monitoring and Follow-up Instructions

• Include instructions for the patient to have renal function tested within 3 months of starting therapy 2, 3
• Schedule follow-up in 2-4 weeks to assess tolerability and consider dose titration 2, 3
• Document baseline renal function (eGFR) in the medical record before prescribing 1, 2

Renal Function Considerations

• Metformin is contraindicated if eGFR <30 mL/min/1.73 m² 1, 2
• For eGFR 30-45 mL/min/1.73 m², use caution and consider lower doses 1, 2
• For eGFR 45-59 mL/min/1.73 m², no dose adjustment is typically needed but monitor renal function more frequently 3, 2

Patient Education Points to Include

• Advise patient about potential GI side effects (nausea, diarrhea) that typically improve over time 4, 7
• Instruct patient to temporarily discontinue metformin for procedures using iodinated contrast, during hospitalizations, or during acute illness 2, 1
• Recommend monitoring for vitamin B12 deficiency with long-term use (>4 years) 3, 7
• Explain that dose may be increased gradually over time to achieve glycemic targets 1, 2

Titration Schedule (if needed)

• If initial dose is well-tolerated, dose can be increased by 500 mg weekly up to a maximum of 2000-2500 mg per day 1, 2
• Daily doses >2000 mg are better tolerated when divided into twice or three times daily dosing 1, 2
• If GI side effects occur during titration, return to previous lower dose and attempt slower titration later 2, 4