I take 1000milligrams - I think it is milligrams, it is that upside down, back to front 'h' symbol that I can never remember the name of - chewable sublingual B12, each day.
I take it first thing in the day, because late at night it makes me have very vivid, disturbed dreams; and I am careful to have a drink of water first, then let it have time to dissolve under my tongue, or between my lip and gum, so as to get the full benefit. Supposedly - and I would guess this is accurate - being well hydrated makes a big difference to cellular uptake of any micronutrient, and the effects of supplementary hydration kick in very rapidly.
I've never had shots, because you basically need to be without a colon before you can get prescribed B12 shots in the UK, so I can't compare the two.
But I certainly notice the lack of B12 even after as little as a day or two without; upping the dosage does not help my energy levels at all.
Of course, when all my other nutrients are going to heck in a handbasket because of malabsorption or electrolyte imbalance, the B12 does nothing at all, because it is simply a catalyst which enables other nutrients to do their jobs; however, I still take it then anyway, on the basis that it maximises the value of any nutrients I do manage to obtain.
Worth noting that there are several forms of B12, cyanocobalamin being only one of them, and supposedly there are advantages/disadvantages to the different ones available. It's a moot point for me as I couldn't find any other form, but you might want to look into that.
Wikipedia's article on B12 was where I started there if I remember correctly.
Good luck !
