Excess B12 does not generally cause direct harm to the kidneys or liver in people with healthy organs
Mol Psychiatry 28:284297 Frost G, Sleeth ML, Sahuri-Arisoylu M, Lizarbe B, Cerdan S, Brody L, Anastasovska J, Ghourab S, Hankir M, Zhang S, Carling D, Swann JR, Gibson G, Viardot A, Morrison D, Louise Thomas E, Bell JD (2014) The short-chain fatty acid acetate reduces appetite via a central homeostatic mechanism
Adjustments to insulin therapy may be necessary to maintain glycemic control
Data are presented as mean SD of three experiments
If you're also taking insulin or sulfonylureas, these may need adjustment to prevent hypoglycaemia when food intake is reduced
Rittenhouse HG, Finlay JA, Mikolajczyk SD, Partin AW