The primary causes of uncontrolled diabetes are poor life-style, infection, ischemic heart disease and inappropriate usage of oral anti-diabetic agents and insulin. Supplementary causes are stroke, acute pancreatitis and endocrine diseases. Multiple endocrine neoplasia type 1 (MEN 1) is an autosomal dominant syndrome characterized by primary hyperparathyroidism, pituitary neoplasia, and foregut lineage neuroendocrine tumors, and is associated with increased glucose levels. We present a case of a 69-year-old woman who had polyuria, polydipsia, weight loss and hyperglycemia over 6 months. She had hypertrophy of the face, hand, and foot, and active bleeding and large folds were observed in the stomach and duodenum upon esophagogastroduodenoscopy. She also had high levels of IGF-1 and gastrin and got the failure of growth hormone suppression after an oral glucose load (75 g). These findings suggested a diagnosis of acromegaly and gastrinoma, which was clinically diagnosed along with MEN 1. The patient improved glycemic control and symptoms after being treated with somatostatin analogues and insulin therapy over a 5-month follow-up period. Here, we report a case of MEN 1 in type 2 diabetes mellitus with a poorly controlled blood glucose level. Clinicians should consider endocrine disease in patients with poor glycemic control in diabetes.