Oops, the RDA is 2.4 mcg B12 daily for adults. however due to poor absorption rates (at least of cyanocobalamin), we could only take in 1.5 to 2 mcg + 1% of B12 per meal orally according to this explanation: https://nutritionfacts.org/video/cheapest-source-of-vitamin-B12/
So taking 250 mcg in supplement form (of cyanocobalamin) per day would be the equivalent of meeting two times the RDA at 4mcg. Not sure what the bioavailability ratio is for the synthesized form of cyano- to the active, natural form of methyl-cobalamin would be. Methylcobalamin is excreted in the urine at about 1/3 less than cyanocobalamin and is 2.5 more potent according to this extremely B12 guy.
I feel like I might not be getting enough B12 from my diet but I have a bottle of methylcobalamin lying around that I feel I could make use of. I just wonder if anyone here can take low doses of methylcobalamin without any problems?
Maybe I should opt to take cyanocobalamin or other forms of cobalamin instead?
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5312744/:
Numerous studies and reviews of B12 metabolism have shown that CNCbl, MeCbl, OHCbl, and AdCbl are reduced to the core cobalamin molecule inside the cytosol. It is important to note that the ligands specific to the ingested B12 form—methyl and adenosyl—are removed during that process and not used inside cells during the conversion of cobalamin to the 2 active forms of B12 (Figure 1).6,25–30 Activation of cobalamin occurs in very specific cellular environments; cobalamin is converted into MeCbl inside the cytosol and to AdCbl inside mitochondria. The final amounts and ratios of MeCbl and AdCbl produced do not depend on the initial form of B12 that had entered the cells.