yes! i've been taking 2500mcg subingual for long as i can remember. a few years ago, our GP tested and said my b12 was very high, and suggested i stopped. i did, and a few months later we saw our ME doc. i told him i'd stopped, and i thought i felt a difference. he said he didn't know why, but once we start it, we can't stop it. so i've been back on it since. it's just an inexpensive one from walmart - https://www.walmart.com/ip/Spring-V...ount/24547733?athbdg=L1102&from=searchResultsMy B12 status truly confuses me. I had it tested recently and it was off the charts (>2,000 pg/ml). I do take some B12, but it is a relatively small amount, all oral, and mostly cyanocobolamin. Folate was normal. The other thing is that when I have had B12 injections, they make me feel horrible: very low energy, lethargic. I'm hoping to retest soon, having stopped taking B12 supplements to see if the high levels are coming from supplementation, as there as some very bad things that can cause high B12 levels.
Does anyone here know if you can get extremely high B12 serum levels from oral supplementation?