The primary action of metformin (a biguanide) is to improve insulin sensitivity. This reduces blood glucose by reducing glucose release from the liver and increasing glucose uptake in tissues (muscle and fat).
1. Therapeutic Considerations with Metformin
All information from medication product monograph unless referenced below.
| A1c Lowering | 1 - 1.5%1 |
| Hypoglycemia Risk | Low |
| Side Effects | Nausea, diarrhea although often well-tolerated if titration is slow. |
| Vascular Protection | Yes |
| Weight | Neutral |
| Cost, Blue Cross coverage; strengths; dosing frequency; indications | |
| Combination Medications | Visit combination meds on Complete Diabetes Medications Table |
| Advice for times of dehydration, vomiting, diarrhea | To avoid concerns with reduced medication clearance, Diabetes Canada advises metformin be stopped until these symptoms are resolved. Adequate hydration should be promoted. |
| Other |
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2. Dosing Considerations with Metformin
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The daily dose of metformin is usually adjusted based on overall blood glucose values or A1c. Most of the combination medications containing metformin are adjusted in the same manner.
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Starting with a low dose and titrating up slowly may help reduce the potential gastrointestinal side effects.
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The dose of metformin is reduced as the eGFR declines. View Diabetes Canada's Therapeutic Considerations for Renal Impairment
References:
1. Inzucchi SE, Bergenstal RM, Buse JB, det al. Management of hyperglycemia in type 2 diabetes: a patient-centred approach. Diabetes Care 2012; 35: 1364-79. http://care.diabetesjournals.org/content/35/6/1364 (Accessed Feb 26, 2018).