Levemir Flexpen is a long-acting analog of insulin used for the treatment of diabetes mellitus. Insulin is a natural substance produced by the pancreas which helps in utilizing glucose for energy production. Patients with diabetes mellitus may not be able to utilize glucose due to the insufficient production of insulin or due to the body’s inability to use insulin or both. This medicine helps in the utilization of glucose and controlling blood glucose levels in such patients. Patients are advised to follow a strict exercise and diet regimen along with this medicine to get the best possible effect.