Does it take long(how many months approx.) to replete b12 levels in human body ?

B12 depletion: depends on several factors including age and overall general health of the individual. Stores of B12 can take 7 years or longer to be depleted in a young person. The important consideration is that once one looses the ability to absorb B12 in the terminal ilium one must do what ever it takes to recover and maintain serum levels and body stores. I shoot for blood levels of 550 or greater.