Metformin usually interacts well with other medications. However, patients should consult their physician before taking any additional prescriptions, over-the-counter medications, nutritional supplements or herbal medications.

Patients who take metformin must be careful to limit their consumption of alcohol, as they can become sick if they consume more than two to four drinks a week.

Other medications that may interact poorly with metformin include:

• Calcium blocking agents. These increase blood and oxygen supply to the heart and include:
  
  

  Amlodipine Bepridil Diltiazem  Felodipine Flunarizine

  Isradipine Nicardipine Nifedipine Nimodipine Verapamil

  
  
• Amiloride, furosemide and triamterene (reduce swelling and fluid retention)
  
  
• Cimetidine and ranitidine (help treat ulcers and other stomach conditions)
  
  
• Dioxin, procainamide and quinidine (heart medications)
  
  
• Morphine (painkiller)
  
  
• Quinine (treats malaria)
  
  
• Trimethoprim (treats urinary tract infections)
  
  
• Vancomycin (antibiotic)
  
  
• Warfarin (anticoagulant)