Metformin is often the first line of therapy for patients with type 2 diabetes: it is relatively inexpensive, available, and has proven efficacy. However, metformin is contraindicated for patients with renal insufficiency, a common comorbidity in diabetes. Do the benefits of metformin outweigh the risks for those with renal insufficiency, or should we use caution when considering metformin for these patients? Dr. Hugh Tildesley, clinical professor in the department of medicine, division of endocrinology at the University of British Columbia at St. Paul's Hospital in Vancouver, Canada, considers the safety of metformin in patients with diabetes. What approach should clinicians use when considering metformin for patients with type 2 diabetes who have some degree of renal impairment? Dr. Lee Freedman hosts.