Hi Tiredlight ;
I now take a sublingual methyl-B12, 5mg. daily. For now it's my maintenance dose. When I had a flare-up a little over a year ago, I had been taking much less, skipping many days. From that I learned I needed a daily supplement.
What finally clued me into the fact that I had a B12 deficiency was that I had enlarged RBC, shown on a CBC as a high MCV and MCH. By the time I had serum B12 measured, it was above the lab's range. Now it's above 3000 pg/ml.
Now I go by symptoms rather than numbers, because the numbers, in this case, don't indicate the dosage that I need to stave off the neuralgia/ neuropathy.
I feel fortunate that I only need a 5 mg. sub. Many people need much more than this, and they also may need injections to better absorb B12. When there is nerve injury in and around the mouth, some people find they are sensitive to sublinguals. (citric acid content). I was sensitve for a time, but the nerves around my mouth,jaw,head have healed and the subs. no longer irritate.