I give myself B12 injections, methylcobalamin--I don't like to do the longer needle that would make it IM injection, so use the 29 Gauge 1/2 " needles, injected them straight in in the upper quadrant of G Maximus.
Dr and pharmacist say result is same. I find these shots invaluable (the sublingual doesn't work for me)--better thinking, colors go from gray(if no shot for a while) to vibrant, see clearer, sharper, more energy, from depression to okay mood, etc etc
My blood levels WAY above the norm, yet still it makes a difference for the better when I take it.
(word of caution--I would not recommend the Cyanocobalamin injectible form--unfortunately used it for quite some time, until realized it has aluminum in it, used in its preparation)