Numbness of the left hand in the middle of the night is usually due to incorrect sleeping posture, cervical spondylosis, carpal tunnel syndrome and other reasons, once found in a timely manner need to seek medical treatment. If the left hand is numb in the middle of the night due to incorrect sleeping posture, it may be related to the incorrect sleeping posture that compresses the blood vessels in the arm or hand, resulting in poor blood circulation, and it may also be related to the compression of the local nerves, which may cause numbness in the hand. Usually, it can be relieved on its own after the compression is lifted, and no special treatment is needed. Cervical spondylosis patients due to herniated discs, may compress the surrounding blood vessels and nerves, resulting in nerve root irritation caused by the symptoms of numbness in the left hand in the middle of the night. Carpal tunnel syndrome patients may appear unilateral or bilateral hand numbness, the most serious symptoms at night or early in the morning, appropriate shaking the wrist can relieve the symptoms. If the symptoms of hand numbness continue to be unrelieved, it is recommended to consult a doctor in a timely manner, under the guidance of the doctor’s active disposal.