Most patients begin to notice the effects in 24 to 72 hours , depending on how deficient they are and what symptoms theyre experiencing
In deficiency, the body makes abnormally large, inefficient cells (megaloblastic anemia)
[1] [2] Factors That Affect How Fast B12 Injections Work Multiple variables influence how quickly you will respond to B12 injection therapy, making it difficult to predict an exact timeline for any individual patient
These studies only show a link between vitamin B12 deficiencies and weight gain, Matthew Cowling, D.O., a physical medicine and rehabilitation specialist in Madison, Wisconsin who specializes in weight loss, previously told The Edge
Note that your blood B12 levels will often normalize before your physical symptoms fully disappear