You may want to do a nasal spray - which is a lot simpler.
I saw the info below online:
For many years after my first small bowel resection, I trudged every month to the gastroenterologist’s office for a B12 injection. I could tell from the slowly accumulating symptoms each month that I had a deficiency. I bumped into walls when walking a straight path, and I inverted words. “Bookkeeping” became “kookbeeping.” Twice a year, the doctor ordered blood tests to make sure my B12 level remained within normal range after the injections.
About 10 years ago, I changed internists. The first thing the new doctor asked me was why I was still getting “those shots” instead of using a weekly nasal spray. If he had had a sample in the office, I probably would have ripped it out of his hands.
This meant no more time off work each month. No more arguing with the insurance company about paying for vitamin injections. No more accumulating symptoms as the month came to an end.
This has been a very good move. I use the spray every Wednesday morning and order 90 days’ worth at a time from my mail-order pharmacy. After checking my B12 levels three months in a row, the internist now orders levels twice a year, and they’re always within normal range.