Hi Joopiter, While MMA is used to detect a shortage of adb12, a lack of high uMMA doesn't preclude response and benefit by taking adb12 and has no bearing at all on a CNS/CSF adb12 shortage. Homocysteine (Hcy) is used as a proxy for evidence of mb12 shortage. Again "normal" Hcy in no way precludes massive benefit from mb12 and again doesn't adress CSF/CNS mb12 levels at all. Neither of these are useful until things are very broken and substantial damage may have been occurring for decades. Plants produce 18 different "junk" cobalamins that can be absorbed as well as cyanocbl that is the excretion form after detoxing cyanide, cobalamin oxidized by nitrous oxide, the rapidly excreted glutathionylcobalamin and no doubt others. Further, the standard testing doesn't distinguish any of these forms nor between adb12 and mb12 and all the many inactive or temporary forms.