Numbness of the right hand when sleeping on the left side may be caused by cervical spondylosis, carpal tunnel syndrome, cerebrovascular disease and other reasons. 1. Cervical spondylosis: If sleeping in an improper posture can cause neck muscle tension and spasm, it may cause compression of the brachial plexus nerve, causing numbness in the right hand. 2. Carpal tunnel syndrome: If the right hand suffers from carpal tunnel syndrome, such as the right hand sleep posture is incorrect, resulting in nerve compression, even if the left side of the sleep will cause the right hand numbness. 3. Cerebrovascular disease: If the sudden cerebral infarction and other diseases caused by the brain’s sensory center or the transmission of sensory nerve bundles are affected, it can cause the right hand numbness. It is recommended that people who sleep on the left side of the right hand numbness to go to the hospital in time, to clarify the cause of the disease, under the guidance of the doctor for standardized treatment, so as not to delay the condition.