To date, no dose-finding study is currently available in literature evaluating the best dose of metformin to administer. In addition, very few data regarding the best protocol for metformin treatment also are available. However, in order to reduce drug-related side effects incidence due to start-up syndrome, metformin is generally administrated with meals at incremental weekly doses until the maximum dosage ranging from 500 to 2550 mg daily; the doses are reduced if side effects appear. This commonly accepted protocol has not been supported by scientific evidences.