I've been self-injecting for a number of weeks now and also take transdermal B12. My symptoms all abated so I started cutting back on the injections to every second day rather than everyday. However, the upper back part of my mouth has become painful and I am wondering if it could be linked to B12 deficiency. Last time my mouth was sore, it was the roof of my mouth and tongue, but I'm wondering if it's possible that the pain would appear in a different place rather than all over. Any thoughts would be most appreciated.