A 68-year-old woman diagnosed with lung adenocarcinoma and brain metastases underwent chemotherapy. She also had type 2 diabetes for approximately eight years, but her HbA1c level was controlled at approximately 7 % without drug therapy. Later, when dexamethasone was added to her chemotherapy regimen, her glycemic control deteriorated, and sitagliptin was started. She also developed cancer cachexia and began treatment with anamorelin hydrochloride, which has ghrelin effects. Thirteen days later, ipragliflozin was started because of elevated blood glucose levels, and four days later, the patient was urgently admitted due to diabetic ketoacidosis (DKA). After hospitalization, the patient discontinued oral medication, and DKA improved with insulin therapy. In this case, the combination of anamorelin hydrochloride and sodium glucose cotransporter (SGLT) 2 inhibitors during chemotherapy with dexamethasone was considered to be the cause of DKA. It is necessary to warn that a combination of these drugs in the terminal stage of cancer may lead to the development of DKA.