SN explained that the Tresiba is a long - acting insulin used to control high blood sugar in adults with diabetes. SN instructed about more frequents side effects of tresiba ( reactions at the injection site, itching, rash, allergic reactions , skin thickening or pits at the injection site ( lipodystrophy ), weight gain, and swelling of your hands and feet, among others). SN oriented to notify the doctor if any of these side effects are severe. SN instructed that the insulin dose may need to change because of change in level of physical activity or exercise, increased stress, change in diet, weight gain or loss, or illness.