The sublingual didn't do much for me personally but that may be because by the time I found out through my own research where some of my health problems might originate, I was too depleted for it to have a noticeable effect.
They tested me for everything under the sun (allegedly) nearly fifteen years ago and my GP sat there with one set of results and said "they're all normal, except your red blood cells are a little large but I don't know what that means?" with a confused expression on her face.
After several months of complete negligence and the practice just not taking my problems seriously, I gave up even trying, I didn't have the energy to waste.
Knowing what I know now, I had also described, many times, all the physical symptoms that are common in pernicious anaemia. I'm quite bitter about the 15 years of my life struggling on an empty gas tank and slowly but surely declining and she couldn't even be bothered to do some fundamental homework for me. I heard the usual....oh it's a natural part of aging but I knew that was absolute rubbish. I used to be so active and unstoppable and like you, had very thick hair which is now probably less than half the thickness it was.
Anyway, by the time I realised I needed B12......15 long years later, the sublinguals just wouldn't cut it for me, or, they just don't work for me personally.
My hair wasn't a priority when I discovered B12 jabs, my energy and mood was, but at the time I made the connection ...... my hair was going through a phase of falling out in quantities I've never seen before, but very soon after a few injections, it stopped completely, just normal shedding now which was a welcome surprise. Kind of scared it might come back but at least it's stopped for now and there's no doubt it was because of the injections, in my mind.
Sorry for rambling on but I hope that helps and gives you a clearer picture