Elderly persons with pernicious anemia should be instructed:

Elderly persons with pernicious anemia, a condition characterized by vitamin B12 deficiency due to lack of intrinsic factor, should be informed about the potential side effects of B12 injections. Diarrhea is a known transient side effect of B12 injections, along with pain and burning at the injection site, and peripheral vascular thrombosis. Increasing dietary intake of B12-rich foods would not be sufficient due to the malabsorption issue in pernicious anemia. Follow-up is essential in managing pernicious anemia, so instructing patients they do not need to return for follow-up is incorrect. While oral B12 may be a suitable option for some cases, it is not the preferred choice for pernicious anemia where malabsorption is the primary issue.