As we all know, diabetic patients should control their diet, but controlling the diet is only controlling and regulating, not dieting or not eating. If inappropriate excessive dieting leads to too rapid weight loss and a decrease in physical fitness, it can easily lead to other diseases. The incidence of herpes zoster is extremely high in diabetic patients and is related to the decreased immune function of diabetic patients; the lowered immune function of diabetes itself, coupled with inappropriate dieting leading to excessive weight loss, makes the occurrence of herpes zoster more likely . Patient a, male, 74 years old, diabetic for 8 years, blood sugar has been stable control, recently in a hospital after treatment, the doctor recommended diet control, within a month weight loss up to 5Kg, but soon appeared herpes zoster, mainly occurred in the face, perioral nasal perimeter obvious, some have extended to the oral cavity, pain is obvious. After admission, he was given nerve nutrition, antibiotics intravenous drip, and Chinese herbal medicine to clear heat and detoxify the body and reduce dampness and swelling. On the second day, the condition still progressed, and considering the patient’s serious condition, he was given methylprednisolone 30 mg intravenous drip, and his condition gradually improved. The patient’s blood glucose did not change significantly after the application of hormones. Respiratory tract infection is also a common complication in diabetic patients, and we have also encountered clinical cases of patients with severe pneumonia complicated by excessive dieting, which is a profound lesson; a similar situation occurred in a diabetic patient admitted recently. Therefore, we remind diabetic patients that diet control is only control, never blindly and unscientifically diet, the purpose of diabetes treatment is overall regulation, not only to control blood sugar, delay complications, but also to improve the quality of life, from a full range of considerations, and more importantly, to follow the advice of the authorities.