Carpal tunnel syndrome is the most common peripheral entrapment neuropathy of the upper limb. Previous experiments found that ultrasound-guided median nerve hydrodissection with 5% dextrose water could ameliorate the condition of carpal tunnel syndrome. Oral administration of vitamin B 12 had been reported to reduce the discomfort from peripheral neuropathy although the level of evidence is not strong. This prospective, double-blind randomized control trial aims to compare the effects of different kinds of the injection agents on carpal tunnel syndrome.