I recently got a Vitamin B12 serum test.
My score was 1137 pg/mL, which is just above the "refence range" of 200 - 1100 pg/mL.
I had been taking a daily oral supplement of 206 mcg. I have now decreased it to 156 mcg per day. I am not interested in injecting anything.
My score was around 1300, so now I am stopping my oral sublingual for a week and taking it every other day or few days.