Once opened, the vial should be resealed properly and returned to cold storage
In a study on 1000 community elderly, it was found that raised tHcy or MMA levels, as well as low holoTC (holotranscobalamin is the circulating form of B12 that is bound to transcobalamin) levels were related to cognitive deficit and reflexes impaired when B12 were within normal range
A slow, controlled injection helps the tissue absorb the liquid more gently, leading to a much more pleasant experience
"Homocysteine and vitamin B12 status relate to bone turnover markers, broadband ultrasound attenuation, and fractures in healthy elderly people"
doi: 10.1093/fampra/cml008
These studies are certainly interesting, but they have yet to conclusively prove a link between large amounts of vitamin B12 and breakouts