My B12 levels are too high

My B12 levels are too high. A Naturopath suggested I take B12 for more energy. I started taking some and within two weeks became anxious and had insomnia. Subsequently I got some bloodwork done and my B12 was flagged (I had trouble understanding the results - so I assumed the flag was because B12 was low). My bloodwork was actually flagged for high B12. I started taking B12 supplements again and once again (roughly 2 months into taking supplements) had the same side effects. My Dr. has since clarified my bloodwork for me and asked me to stop taking the supplements. Everything has returned to normal, however, if I incorporate foods high in B12 in my diet (I'm not currently Vegan - or rather I wasn't....) - the symptoms return. My bloodwork B12 is only 989 pmol/L - so it's not crazy high, but it just doesn't work well with me. I am now on a strict diet of veggies and carbs only. My question - how long should it take for my B12 levels to drop by 100 pmol/L? And if I remain on a strict veggie/carb diet...when (timeframe) would I need to get B12 rechecked (years from now?) in case B12 becomes too low?

It's probably safe to get your blood checked regularly (every few months? I don't know, since I'm not a doctor) until your results become stable, and then, check again after starting any new supplements or changing your diet. It sounds like you might just not need a B12 supplement (not all vegans do), but you should check just to be safe.