Thank you for your question. Low vitamin B12 can be due to a type of anemia called pernicious anemia which is the decreased absorption of B12 in the terminal ileum of the intestine, or due to decreased dietar intake of B12. As a result, there would be a decrease in red blood cell quantity and remaining RBCs would be larger in morphology referred to as megaloblastic. It is possible that you may have a subclinical form of B12 deficiency, which produces symptoms, but not severe enough to show morphological changes in your RBCs. The diagnosis of B12 deficiency is using a combination of your symptoms, B12 levels, and other laboratory findings. The range of B12 can vary depending on one's diet or if there is a history of chronic illness.
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