However, a common, potentially damaging, and well-documented complication of metformin—vitamin B12 malabsorption—is poorly recognized and not screened for or treated prophylactically by the majority of physicians who prescribe metformin. This is unfortunate since a correctable cause of irreversible damage to the central and peripheral nervous system may be overlooked. In this article, I present a case of peripheral neuropathy that could have been avoided by the monitoring of vitamin B12 levels or by prophylactic annual vitamin B12 injections. Furthermore, at presentation the neuropathic symptoms and clinical findings could have been misdiagnosed as being due to diabetic neuropathy, which would have further prolonged the time to diagnosis and treatment of the neuropathy and resulted in further neurological damage.