. ♪ and a vial. use a syringe levemir® flexpen comes prefilled with long-acting insulin taken once daily for type 2 diabetes to help control high blood sugar. dial the exact dose. inject by pushing a button. no drawing from a vial. no refrigeration for up to 42 days. levemir® (insulin detemir [rdna origin] injection) is not recommended to treat diabetic ketoacidosis. do not use levemir® if you are allergic to any of its ingredients. the most common side effect is low blood sugar, which may cause symptoms such as sweating, shakiness, confusion, and headache. severe low blood sugar can be serious and life threatening. ask your health care provider about alcohol use, operating machinery, or driving. other possible side effects include injection site reactions. tell your health care provider about all medicines you take and all of your medical conditions.