Allergic reaction to human insulin is uncommon. But they can cause mild to severe symptoms such as dyspnea, hypotensive shock, etc. Here we report the case of a patient with type 2 diabetes and insulin allergy successfully managed with desensitization. A 60-year-old man with insulin allergy was transferred. He had poorly controlled type 2 diabetes (fasting blood glucose 230 mg/dL). He developed itching sense and erythema at the injection sites of human insulin in a few minutes. And serum IgE level was elevated to 1618.0 IU/mL. The insulin was changed to other preparations, including short and long-acting insulin analogues, with similar responses. He was commenced on twice a day injection protocol in addition to his oral hypoglycemic agents, and achieved fair control (fasting blood glucose 100 mg/dL) on 24 units of Novomix Flex Pen per day, with little or no skin or systemic reaction. This is the case report of insulin allergy in type 2 diabetes being successfully managed by desensitization.