This page covers both, with the oral route first
PMC 5683008
These patterns inform our current protocols: pre-injection metabolic screening (TSH, ferritin, B12, vitamin D), mandatory injection-site rotation education, and 12-week check-ins to address lifestyle factors
If you take vitamin B12 supplements, let your doctor know so they can tell you how much you need, and make sure they won't affect any medicines you're taking
You cannot take in too much Vitamin B12, any excess in your system will simply go through your digestive tract, unabsorbed, and will be flushed out in your trips to the restroom
Relief from symptoms usually begins within a few hours, but complete healing may take a few days to weeks