Sudden hand numbness may be caused by postural discomfort, cervical spondylosis, carpal tunnel syndrome and other reasons. 1. Postural discomfort: If you keep the same posture for a long time or your hands are under pressure, it may cause poor local blood circulation, resulting in sudden numbness of the hands. 2. Cervical spondylosis: after suffering from cervical spondylosis, due to the upper limb nerves in the cervical nerve root compression, hyperplasia bone or herniated intervertebral discs, calcified ligaments stimulation, compression, nerve root conduction is weakened, resulting in sudden numbness of the hand. 3. Carpal tunnel syndrome: the nerve passes through the wrist, there is a median nerve, when the carpal tunnel stenosis occurs, resulting in the soft tissue inside the carpal tunnel hyperplasia, squeezing the nerve, it will be manifested as sudden numbness of the hand. There are many other causes of sudden hand numbness, such as hyperlipidemia and cerebral infarction. Patients should go to the hospital in time to identify the cause of the disease and targeted treatment.