I'm curious what could happen to people who have pernicious anemia but are intolerant to b12?

Vit b12: if you have pernicious anemia- and you do not take replacement of vit B12- your vitamin b12 obviously will continue to go down . anemia, weakness, fatigue, memory problem, forgetfulness , neuropathy, dementia can happen with significant vitamin b12 deficiency- and those can become permanent if you do not take supplement of vit b12. what do you mean by intolerance? you can get via IM, sublingual .

You need B12: If you have pernicious anemia, you need to take Vitamin B12 because your body does not absorb this vitamin. Vitamin B12 is a water-soluble vitamin that is usually very well tolerated, and non-allergenic. In patients that have pernicious anemia, B12 is usually given intramuscularly by injection once a month, and many patients administer it to themselves. It can also be given intranasally.