You have medical conditions such as pernicious anemia or malabsorption issues, which prevent proper Vitamin B12 absorption
Many nutrients have their action INSIDE the cell, which means that testing serum and blood levels just give us an indication of what may be available but that is assuming everything else is working properly: cellular activity, enzyme activity, receptor activity, etc
While most people tolerate B12 shots well, it is always best to stay in communication with a qualified medical team
These changes occurred through direct effects on adipocyte biology rather than appetite suppression, as research models maintained normal feeding behavior while exhibiting significant reductions in individual adipocyte size
tests to measure blood levels of methylmalonic acid (MMA) or homocysteine, both of which may be sensitive indicators of vitamin B12 deficiency