Editing Intrinsic factor (section)

=== Treatment ===

In most countries, [[intramuscular injection]]s of vitamin B<sub>12</sub> are used to treat [[pernicious anemia]].<ref name="Shipton_2015" /> Orally administered vitamin B<sub>12</sub> is absorbed without intrinsic factor, but at levels of less than one percent than if intrinsic factor is present.<ref>{{cite journal | vauthors = Alpers DH | title = What is new in vitamin B(12)? | journal = Current Opinion in Gastroenterology | volume = 21 | issue = 2 | pages = 183–186 | date = Mar 2005 | pmid = 15711210 | doi = 10.1097/01.mog.0000148331.96932.44 | department = (review) }}</ref>  Despite the low amounts absorbed, oral vitamin B<sub>12</sub> therapy is effective at reducing symptoms of pernicious anemia.<ref name="Andres_2010">{{cite journal | vauthors = Andrès E, Fothergill H, Mecili M | title = Efficacy of oral cobalamin (vitamin B12) therapy | journal = Expert Opinion on Pharmacotherapy | volume = 11 | issue = 2 | pages = 249–256 | date = Feb 2010 | pmid = 20088746 | doi = 10.1517/14656560903456053 | s2cid = 37088496 | department = (review) }}</ref>

Vitamin B<sub>12</sub> can also be given [[sublingual administration|sublingually]], but there is no evidence that this route of administration is superior to the oral route,<ref name="Sharabi_2003">{{cite journal | vauthors = Sharabi A, Cohen E, Sulkes J, Garty M | title = Replacement therapy for vitamin B12 deficiency: comparison between the sublingual and oral route | journal = British Journal of Clinical Pharmacology | volume = 56 | issue = 6 | pages = 635–638 | date = Dec 2003 | pmid = 14616423 | pmc = 1884303 | doi = 10.1046/j.1365-2125.2003.01907.x | department = (primary) }}</ref> and only Canada and Sweden routinely prescribe this route of administration.<ref name="Shipton_2015">{{cite journal | vauthors = Shipton MJ, Thachil J | title = Vitamin B12 deficiency - A 21st century perspective | journal = Clinical Medicine | location = London, England | volume = 15 | issue = 2 | pages = 145–150 | date = Apr 2015 | pmid = 25824066 | pmc = 4953733 | doi = 10.7861/clinmedicine.15-2-145 | department = (review) }}</ref>

Because vitamin B<sub>12</sub> absorption is a multistep process that involves the stomach, pancreas and small intestine, and is mediated by two carriers: [[Haptocorrin]] and intrinsic factor, and because [[Haptocorrin]] ([[Transcobalamin|transcobalamin I]]) binds to vitamin B<sub>12</sub>, and  Vitamin B<sub>12</sub> is acid-sensitive, when vitamin B<sub>12</sub> binds to [[Haptocorrin]] it can safely pass through the acidic stomach to the duodenum, given time in the mouth.<ref name="Fedosov_2012" />