Unlike oral supplements, which must pass through the digestive system and may be poorly absorbed, B12 injections bypass the gut entirely
He responded that there would be no harm with my beginning monthly injections of B12 alongside my hormone replacement and supplemental vitamin D
Lenny Macrina: Right
[115] This functionality is lost in vitamin B 12 deficiency, resulting in an increased homocysteine level and the trapping of folate as 5-methyl-tetrahydrofolate, from which THF (the active form of folate) cannot be recovered
You do need bioavailable active forms of vitamin B12 like methylcobalamin, adenosylcobalamin, or hydroxocobalamin
While traditionally described as being absorbed directly through the mucous membranes in the mouth, research suggests that much of the dose is actually swallowed and absorbed through the digestive system via passive diffusion, similar to standard oral tablets