tresiba® is a long-acting insulin used to control high blood sugar in adults with diabetes. don't use tresiba® to treat diabetic ketoacidosis, during episodes of low blood sugar, or if you are allergic to any of its ingredients. don't share needles or insulin pens. don't reuse needles. the most common side effect is low blood sugar, which may cause dizziness, sweating, confusion, and headache. check your blood sugar. low blood sugar can be serious and may be life-threatening. injection site reactions may occur. tell your prescriber about all medicines you take and all your medical conditions. taking tzds with insulins like tresiba® may cause serious side effects like heart failure. your insulin dose shouldn't be changed without asking your prescriber. get medical help right away if you have trouble breathing, fast heartbeat, extreme drowsiness, swelling of your face, tongue or throat, dizziness or confusion. i found my tresiba® reason. find yours. ask your diabetes care specialist about tresiba®.