Left hand numbness may be a sign of cervical spondylosis, due to cervical spine strain, osteophytes, disc herniation, can compress the spinal cord and nerve roots, can cause upper limb weakness, numbness of the fingers, may also be accompanied by pain in the upper limbs, dizziness and nausea, etc., you can take cervical spine film examination to confirm the diagnosis. May also be a sign of diabetes, you can check the blood sugar, urine sugar, etc. to confirm the diagnosis, diabetic patients due to long-term blood sugar abnormalities, can lead to peripheral neuropathy, numbness of the limbs, may be accompanied by gangrene, wounds are not easy to heal and other symptoms.