After waking up left hand numbness, may be incorrect with the sleeping position, may also be due to cervical spondylosis, acute cerebrovascular disease and other reasons. 1. Incorrect sleeping posture: when sleeping, if you keep an incorrect sleeping posture for a long time, resulting in the left arm for a long time pressure, resulting in the arm of the side of the blood circulation is not good, will wake up after the left hand numbness. Through appropriate activities, release the compression, will help to make the symptoms disappear soon. 2. Cervical spondylosis: patients with this disease sleep due to improper sleeping posture, or pillow is not appropriate, resulting in neck muscle tension, spasm, resulting in local nerve root compression, may cause numbness in the left hand after waking up, may also be accompanied by numbness of the upper limbs, weakness, neck and shoulder discomfort and other symptoms. 3. Acute cerebrovascular disease: left hand numbness after waking up, if continued to be unable to relieve, accompanied by unfavorable speech, numbness of the left lower limbs, weakness and other symptoms, should be alert to the possibility of acute cerebrovascular disease may be. After waking up with numbness in the left hand, if the symptoms continue to be unable to improve, should be taken seriously, timely medical care, clear cause and timely treatment.