Hi Anniekim, Fredd, when you write 'I appear to have restricted, not absent, conversion of one type of cobalamin to another' and Rich has commented that you have shared you have an inborn genetic error of metabolism in your intracelluar B12 processing enyzymes, am I right in understanding you have deduced this not through tests, but through your own self treatment trials? Yes. This deduction, or maybe induction, was arrived at via a detailed lifetime history and various changes in practice along the way. Most babies who have a severe and complete lack of such processing die young or have severe "failure to thrive" and other such problems. The testing just isn't done on adults so the discovery of adults with this disorder is "rare". I didn't have a severe reaction until I entirely removed meat from my diet by becoming vegetarian. Even though not vegan the little I got from eggs, dairy and occasional fish didn't make much difference. I had separate responses to body-mb12, body-adb12, high dose CNS-mb12 and high dose CNS-adb12, but then so do many people here. It is that separate CNS response adb12 and/or mb12 that appears to differentiate FMS, CFS, Parkinson's, Alzheimer's?, ALS and MS.