Complications of diabetes mellitus in the elderly include acute severe metabolic disorders, infectious diseases and chronic complications. 1. Acute severe metabolic disorders: the most common are diabetic ketoacidosis and hyperosmolar hyperglycemia syndrome, which are often triggered by infections, traumas, dehydration, and so on. 2. Infectious diseases: pyelonephritis, cystitis, fungal vaginitis, etc. are most common in elderly female patients, and tuberculosis and perianal abscess are also common in the elderly. 3. Chronic complications: diabetic microangiopathy, such as diabetic nephropathy and diabetic retinopathy, mostly seen in patients with diabetes mellitus for more than 10 years; diabetic macrovascular lesions, diabetic neuropathy, diabetic foot and other elderly diabetic patients are often seen, manifested as atherosclerosis, numbness of the hands, numbness of the feet, foot ulcers and so on. Therefore, elderly diabetes involves more complications, patients should consult the doctor in time, early treatment, so as not to delay the condition.