because there just might not be one. but i've learned a lot from patients who use flexpen. flexpen comes pre-filled with the insulin i take and i can dial the exact dose of insulin i need. i live my life on the go and need an on-the-go insulin. i don't need to carry a cooler with flexpen. novolog is a fast-acting, man-made insulin used to control high blood sugar in adults and children with diabetes. do not inject novolog if you do not plan to eat within 5 to 10 minutes after injection to avoid low blood sugar. tell your healthcare provider about all medicines you take and all of your medical conditions, including if you are pregnant or breastfeeding. the most common side effect of novolog is low blood sugar. other possible side effects include reactions at the injection site. get medical help right away if you experience serious allergic reactions, body rash, trouble with breathing, fast heartbeat or sweating. ask your healthcare provider about novolog flexpen today.