Anemia, MegaloblasticAnemia, PerniciousAnemia, MacrocyticIntrinsic FactorGastritisVitamin B 12 DeficiencyVitamin B 12Folic Acid DeficiencyAnemiaMegaloblastsHydroxocobalaminThiamineSchilling TestAchlorhydriaGastritis, AtrophicFIGLU TestFolic AcidAnemia, HypochromicPregnancy Complications, HematologicMalabsorption SyndromesHomocystinuriaDeoxyuridineGastric MucosaBone Marrow Examination5-Methyltetrahydrofolate-Homocysteine S-MethyltransferaseCobalt IsotopesAnemia, AplasticVitamin B ComplexGastrinsDiphyllobothriasisParietal Cells, GastricPostgastrectomy SyndromesAnemia, HemolyticGastric JuiceTranscobalaminsPancytopeniaHearing Loss, SensorineuralFanconi AnemiaHelicobacter pyloriStomachGastroscopyBlood Group AntigensErythropoiesisHelicobacter InfectionsAnemia, Hemolytic, AutoimmuneMethylmalonic AcidConsanguinityStomach NeoplasmsIntestinal AbsorptionMembrane Transport ProteinsAutoimmune DiseasesBone MarrowCarcinoid TumorEnterochromaffin CellsErythrocytesBloodAutoantibodiesZollinger-Ellison Syndrome