https://blogs.mercola.com:443/sites/vitalvotes/archive/2004/11/07/Special-Test-Needed-For-Vitamin-B12-Deficiency.aspxVitamin B12 is the largest vitamin and because it is so large it can not be absorbed too well orally. As many peoiple age they lose the ability of their stomach to make intrinsic factor and this can contribute to vitamin B12 deficiency. B12 deficiencyenCommunityServer 2008.5 SP1 (Debug Build: 31106.3070)