b12 injection versus pill Pills vs B12 Shots B12 Injections or Oral B12:

Think this might be you

How often are vitamin B12 injections administered during the initial loading phase

[9] A related cause is reduced stomach acid production with age or from long-term use of proton-pump inhibitors, [10] H 2 blockers, or other antacids, [11] and interaction with metformin

NA cannot be salvaged into NAD + any longer if it is N-methylated by NNMT, so the methylation of NA impairs the abundance of free NAD + and then affects the activities of these NAD + -consuming enzymes [19]

"High prevalence of folic acid and vitamin B12 deficiencies in infants, children, adolescents and pregnant women in Venezuela"