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Hi John,
Pernicious anaemia is due to the inability of the gastric mucosa to
absorb B12. It is not specifically related to celiac disease, but celiac
disease can prevent absorption of B12 and folic acid (and other things).
Whether you will need B12 injections for life depends on whether your
lack of B12 is due to celiac disease (in which case, the gut may well
recover after a sufficient time on a g.f. diet) or to another cause.
Folic acid is usually very safe, but there have been reports of nausea,
flatulence, diarrhoea, irritabiility, sleep disturbances, rash,
bronchospasm. The most important thing to know is whether your anemia is
due to lack of B12, folic acid or both.