Unconscious fainting may be caused by hypoglycemia, insufficient blood supply to the brain, cardiac arrhythmia and other diseases. 1. Hypoglycemia: Hypoglycemia is a group of syndromes characterized by low blood glucose concentration, sympathetic nerve excitation and hypoxia of brain cells. Symptoms are usually manifested as sweating, hunger, panic, trembling, pallor, and even coma. 2. Insufficient blood supply to the brain: Insufficient blood supply to the brain means that the blood supply to a certain part of the human brain is insufficient, which leads to the dysfunction of brain function. Because of external stimulation, pain and own discomfort, it causes vasovagal reflex, which leads to the decrease of return blood volume and transient insufficient blood supply to the brain, thus causing unconscious fainting. 3. Arrhythmia: Arrhythmia is a general term for irregular, fast or slow heartbeat caused by abnormal electrical conduction function of the heart. It may cause palpitations, dizziness or even fainting and sudden death. The condition of unconscious fainting may also be caused by other reasons, and it is recommended that the patient immediately consult a doctor for a detailed examination and timely treatment.