Low B12 usually means that either you donât intake the vitamin in enough dosage with food or it is not absorbed well by the intestines. Lack of the vitamin B12 may cause megaloblastic anemia; thatâs probably why your doctors asked you for a blood test. If megaloblastic anemia is caused by chronic stomach inflammation (lack of intrinsic factors withstanding), it is called "pernicious anemia". If the blood analyses find anemia, you will most likely be asked to intake B12 parenterally (by injection).