Veganism, for example, is more common in todays society and with B12 normally being obtained from liver, milk, eggs, fish, oysters and clams a B12 injection is an alternative method of ensuring your body still receives these essential vitamins
Just be sure you stick to quality supplement brands that dont contain weird fillers
You can, but not everyone absorbs oral supplements well, especially those with digestive or absorption issues
Liposomal formulations may improve penetration and stability
They certainly expected this criteria to be immutable though
NNMT (nicotinamide N-methyltransferase) is an enzyme found in fat cells and other tissues that can become overactive in certain metabolic conditions