Low intrinsic factor in gut that hampers absorption, pernicious anemia, parasites in the gut, diet poor in Vit B12, Crohn;s disease, IBS,
or poor metabolism by liver are the causes behind it. The hands could be cold due to reduced blood supply as in diabetes, carpal tunnel syndrome, chronic fatigue syndrome, poor sleep, smoking, Raynaud’s phenomenon and pinched cervical spinal nerve.