Left hand index finger numbness, may be a complication of diabetes, long-term diabetes, caused by the body sugar, fat metabolism disorder, prone to peripheral neuropathy, but also cause limb blood circulation disorders, resulting in numbness of the fingers. Cervical spondylosis can also lead to numbness and pain in the fingers, cervical spondylosis, herniated discs will compress the nerves, causing pain in the upper limbs, numbness, dyskinesia, you can take cervical spine film to confirm the diagnosis, as well as traumatic injuries caused by nerve damage, can cause numbness, and promptly to the hospital for treatment.