Companies get around this by labeling it as a "research chemical not for human consumption." This means the product is completely unregulated, and you have no way of knowing if it's pure, sterile, or even contains the correct substance
However, do not stop prescribed B12 injections or tablets for confirmed deficiency (such as pernicious anaemia) without consulting your GP, as this could lead to serious health consequences
Yoon HS, Cho CH, Yun MS, Jang SJ, You HJ, Kim JH, et al
CrossRef Hydrogen Nano-Bubble Water Suppresses ROS Generation, Adipogenesis, and Interleukin-6 Secretion in Hydrogen-Peroxide- or PMA-Stimulated Adipocytes and Three-Dimensional Subcutaneous Adipose Equivalents Li Xiao, Nobuhiko Miwa Cells.2021
The most obvious solution, oral or intravenous glutathione, does not work effectively and neither does N-acetylcysteine
Clin Exp Rheumatol, 1996