The signs of numbness in the left hand are related to cervical spondylosis, peripheral neuropathy, nerve injury and coronary heart disease. 1. Cervical spondylosis: cervical disc degeneration, cervical hypertrophy and hyperplasia will cause cervical nerve root compression, followed by unilateral numbness of the fingers, numbness of both fingers and other symptoms, and sometimes the whole arm will be numb and painful. 2. Peripheral neuropathy: after the occurrence of peripheral neuropathy, the peripheral nerves of the left hand will be violated, including local blood supply disorders and lack of vitamins in the body, and then the left hand will be in anesthesia. 3. Nerve injury: whether it is related to the local nerve affected by trauma, such as frequent sports and injuries when the local nerve is affected, which can easily lead to the left hand paralysis, including the wrist Hall syndrome, which will aggravate the numbness of the arm. 4. Coronary heart disease: atypical symptoms of left upper arm, shoulder pain and numbness. More diseases that cause numbness in the left hand, it is recommended to go to the hospital for timely consultation, under the guidance of the doctor to determine the treatment program, to avoid blindly using medication on their own.