New England Journal of Medicine , 389(6), 514526
All are quick IM injections, ~15 minutes
There may be instances where certain conditions, such as poor nutrition, intestinal issues, infections, and cancer, may lead to B12 deficiency
It is listed as a rare adverse reaction in UK product information for both oral and injectable B12 preparations, and most people tolerate B12 supplements well even at high doses
Reference ranges vary slightly between laboratories, but the general framework used by most U.S
Seek medical help if you experience any allergic reactions