The dosage depends on the severity of the condition and the patients overall health
So, you measure a higher B12, but part of that B12 is inactive, so useless Oral B12 supplementation, even in the form of a multivitamin preparation, may result in serum B12 concentrations just within the normal range without abolishing symptoms
Oral, sublingual, and injectable forms may be discussed differently in clinical or wellness settings, but dosing should not be adjusted without guidance from a qualified healthcare provider
In people with conditions like hemochromatosis (iron overload), this can be dangerous and lead to organ damage
"Nascobal (Cyanocobalamin, USP) Nasal Spray 500 mcg/spray 0.125 mL Rx only" (PDF)
Intramuscular injection can cause local pain, deep (gluteal) injection is necessary