Here is my conclusion on the research I have done so far.
Methyl.-B12 is very experimental at this stage in the game. It depends on body weight and especially level of activity. Some burn it off much faster then others, so needs very widely from one individual to another. It has been proven to be more effective with subcutaneous injection rather then the standard intramuscular rout. Subcutaneous allows for slower and steady release, so as to have less excess that will get dumped. This is because in the first few hours the body will dump any excess. On the other hand, intramuscular gives the fastest, most immediate response. There are no known toxicity levels ever published or set. IT has been suggested that a dose of aprox. 30 mcg per 1 lb of body weight is not too high of a dose, if given subcutaneously, every 3 days.
From my personal experimentation with cyano.-B12, with a solution of 1000 mcg/ml dose at 1000 mcg (1 cc) [1 cc = 1 ml = 1 mg] and intramuscular, a sickish feeling was noted aprox. 1 hour after injection, with slowly feeling better over next many hours and feeling the best over the next 2 days. No symptoms at 500 mcg (.5 cc) intramuscular.
I plan a first test run of 500 mcg (.5 cc) intramuscular every 3 days to start, then will up-dose and lesson or increase frequency as tolerated, then test with subcutaneously.