My labs for b12 were 1823pg/ml. is this concerning as the reference range was 206-911?

High B12 levels pose no danger and excess amounts are simply excreted in the urine. B12 is a water soluble vitamin. I assume you're taking B12 orally or sublingually rather than by injection. 1000 units per day is a reasonable oral or sublingual dose but can probably be reduced to 500 units per day or even less.unless you have had a history of B12 deficiency.