There's no question that parenteral B12 works in pernicious anemia, but the lack of intrinsic factor in this illness impairs not only absorption, but it also impairs re-absorption of B12 which is secreted in the bile in the so-called enterohepatic circulation. Thus, the usual maintenance dose of 1000 mcg im or s/c monthly may not be enough to prevent cognitive impairment. I would consider a weekly dose of 1000 mcg as a better bet. Alternatives to parenteral B12 include oral (I suggest 1000 mcg twice a day, as only about 1% of an oral dose is absorbed via passive means, and again, losses of B12 are higher in those lacking intrinsic factor), or intranasal spray (500 mcg per spray of hydroxocobalamin; use one spritz daily). This last product has much better absorption than oral preparations, but is only available online from the U.K., the last time I checked. It should not be confused with sublingual sprays, however.

Thank you sir.

Hi Emmanuel

In pernicious anemia, there is decreased absorption of vitamin B12 due to lack of intrinsic factor . This is caused by the autoimmune destruction of gastric parietal cells which produce intrinsic factor. Hence, the only treatment is to supplement vitamin B12. Oral supplementation is not effective as intrinsic factor is not available for its absorbtion. Hence, parental route (Intramuscular injection) will be used to administer vitamin B12. Initially, it is given one every other day. However, over time it may be cut back to once per week or once per month. Other than IM administration, vitamin B12 may also be given as pills (some of it may still be absorbed), or nasal spray or gel, or through sublingual route. eating foods that are rich in vitamin B12 may also make the person feel a bit better. Thank you

The short answer is "No". There is no cure unless the cause is dietary via extreme veganism. Parental B12 is the answer to prevent both haematological and neurological deterioration.

If B12 deficient or supplemental treatment naive, take Methylcobalamine 5000 mcg/day sublingual for 60 days, then 1/week for your whole life. Check B12 blood level only after 10-14 days break. In Japan range is much higher (500-1300 nmol/l or 677-1761 pg/ml) which explains why dementia is so rare in Japan. https://www.mthfrsupport.com.au/vitamin-b12-reference-range-level-set-low/

If you take the shots of B12 thus doesn’t mean you are going to retain all. For cyanocobalamine retention is around 15%. For hydroxicobalamine is 71%. If taken by mouth and low/no intrinsic factor you can rely only on passive absorbtion which at a 1000 mcg dose is around 1% (10 mcg) which should be sufficient for 4 days in an adult (no pregnancy, no breast feeding) because the RDA is 2.4 mcg (2,6 in pregnancy and 2.8 in breast feeding mothers)

The world of micronutrients still has many gaps, and the specific case of vitamin b12 is particularly complex given the clinical importance of its levels, which are low, but also high. In this sense, in complement to the debate question, I want to share with you the following manuscript detailing the aspects associated with high levels of vitamin b12.

Article Hipervitaminosis B12 una mirada desde la atención primaria