After extensive review of the evidence, through a literature search spanning the years 1966 through 2010, the society concluded that metformin should be the primary drug of choice when lifestyle methods have failed to bring about glycemic control for patients.
Metformin, which has been in use for over 40 years, was found to have fewer side effects than drugs that cause the pancreas to secrete insulin and to be more effective in reducing A1C compared to other agents when taken alone or in combination with other drugs.
One of the most widely prescribed glucose lowering agents in use, its major effect is a reduction in insulin resistance. It lowers levels of glucose in the blood by decreasing the liver’s output of glucose. (The liver in people with diabetes often secretes an overabundance of glucose relative to the body’s needs, releasing approximately three times more glucose than in those without diabetes.)
Metformin also improves uptake of glucose by the muscle cells.
The medication does not generally cause hypoglycemia (low blood glucose), unlike many other oral agents. It has also been shown to be weight neutral (meaning it won’t cause you to put on pounds) and has a positive effect on cholesterol levels.
Metformin is generally used in the treatment of type 2 diabetes, but can also be used in conjunction with insulin in those patients with type 1 who are overweight. Caution is advised in using the drug in patients with impaired kidney function and in the elderly due to the possibility of lactic acidosis, or too much lactic acid in the bloodstream.
Recommendations from the ACP include:
- Use metformin as the first drug of choice when lifestyle measures such as diet and exercise have failed.
- Use metformin as the first drug of choice along with lifestyle measures to treat most patients with diabetes
- Add another medication along with metformin when patients have persistent high blood glucose levels.
The guidelines are similar to those promoted by the Joslin Diabetes Center which recommends consideration of metformin along with lifestyle modification as an initial approach to those with type 2 diabetes.