Vitamin B12 is necessary for DNA synthesis, red blood cell development, and immune function
This leads many people to ask the question, How many B12 tablets do I need to take to equal one B12 injection? Its not actually that simple
The initial management of overdose: After a careful clinical evaluation of the patient the importance of time elapsed since last ingestion or administration, the amount of poison swallowed and discarding the contraindication of certain procedures, the professional will decide whether or not the treatment of general rescue: emesis or gastric lavage, activated charcoal and saline purgative (45 to 60 minutes after the activated carbon), hemodialysis
Additionally, the issue is exacerbated by traditional laboratories setting the 'normal' range too low, which may result in undiagnosed B12 deficiencies
Oral vitamins must get broken down by the GI tract (through stomach, intestines) then go through the liver for metabolizing