Recommended daily requirement of vitamin B12:
>500μg
Studies have shown that oral vitamin B12 at daily doses of 1000μg is effective for treatment of vitamin B12 deficiency even in the absence of intrinsic factor, an acidic environment, or terminal ileum resection. There is strong evidence of an alternative pathway to the the usual intrinsic factor/terminal ileum pathway but doses of 500μg or less are only variably absorbed via this pathway so need higher doses.