Low fasting blood glucose may be related to diet, exercise, medication and disease. 1. Diet and exercise: Excessive dietary control or heavy exercise before bedtime may also cause low fasting blood sugar. 2. Pharmacologic factors: diabetic patients using too large a dose of hypoglycemic drugs can also cause low fasting blood sugar. 3. Diseases: insulinoma secretes too much insulin, adrenocortical insufficiency secretes not enough corticosteroid, etc., all of which can lead to fasting hypoglycemia. Fasting low blood sugar may not have obvious symptoms, may also appear panic, sweating, hunger and other discomforts, it is recommended to consult a doctor in time to clarify the cause of the disease, under the guidance of the doctor treatment.