There are various reasons for being B12 deficient, to name a few,
Pernicious Anemia
Atrophic gastritis, in which your stomach lining has thinned Conditions that affect your small intestine, such as Crohn's disease, celiac disease, bacterial growth, or a parasite
Immune system disorders taking certain medications that interfere with the absorption of B12. This includes some heartburn medicines including proton pump inhibitors (PPIs)
if you follow a vegan diet or you are a vegetarian who doesn't eat enough eggs or dairy products to meet your vitamin B12 needs.
Now, my B12 deficiency is due to my vegan diet ( I made a mistake of not taking B12 supplement for the last 7 years)
My level is 99 pg/ ml and I have started loading shots of hydroxycobalamine every other day. Soon I will taper it down to once a week for at least 6 to 8 weeks.
A while ago, you would have caught me curled up with a nice detective novel but now, I am so shaken up, most of the time on this forum getting as much info as possible.
But is it a good idea to read posts of someone with PA or Atrophic gastritis etc? Comparing apples with oranges? I wish it was possible to create cause specific B12d threads, that will help us better.
With my brain fog and age ( 65) I have no idea how to do that. I don't know how to effectively use search tool, if I type vegan I don't get any useful info.
Any suggestions?