Slight numbness in the left half of the body may be related to improper sleeping position, or it may be caused by intracranial space-occupying lesions, cerebrovascular diseases and other reasons. 1. Improper sleeping position: If you keep lying on your side for a long time, the left half of your body will be pressurized for a long time, resulting in poor blood circulation on the pressurized side, which may cause slight numbness of the left half of your body, and the symptom will disappear soon by changing the sleeping position and appropriate activities, without special intervention. 2. Intracranial space-occupying lesions: Due to the existence of space-occupying lesions in the skull, it is easy to lead to increased intracranial pressure, resulting in local neurological dysfunction, which may cause slight numbness of the left side of the body, and may be accompanied by headache, vomiting and other symptoms. Common diseases include brain tumor, brain abscess, brain parasitic disease and so on. 3. Cerebrovascular disease: common in cerebral hemorrhage, cerebral infarction, etc., due to local bleeding or ischemia of brain tissue, resulting in damage to brain nerves, causing cerebral dysfunction, may show slight numbness of the left side of the body, may also be accompanied by unfavorable speech, difficulty in swallowing and other symptoms. Slight numbness of the left side of the body may also be caused by other reasons. If the symptoms continue to be unrelieved, you should consult a doctor as soon as possible for a clear diagnosis of the cause, and then be guided by a doctor for treatment.