Table 1:

Characteristics of B₁₂ deficiency in infants

Causes	Infants whose mothers’ diets are deficient in B₁₂^*	Infants whose mothers have pernicious anemia
Presentation	Macrocytic anemia, failure to thrive, lethargy, hypotonia, hyperreflexia, loss of milestones, microcephaly, irritability, glossitis14,15
Diagnosis	Megaloblastic anemia in infant Low serum B₁₂ in infant and mother Maternal history of diet low in B₁₂	Megaloblastic anemia in infant Low serum B₁₂ in infant and mother Positive Schilling test in mother or history of maternal pernicious anemia
Treatment	Cyanocobalamin (intramuscular or intravenous injection) daily, then tapered to weekly and monthly17 Early introduction of B₁₂-fortified foods (e.g., cereals or formula)
Prevention	Maternal oral supplementation of B₁₂ Oral supplementation of vitamin B₁₂ Early introduction of B1₂-fortified foods23	Maternal oral or intramuscular cyanocobalamin Early introduction of B₁₂-fortified foods^†

↵* For example, vegan or vegetarian diets.
↵† We are unaware of recommendations on oral B₁₂ supplementation for prevention in infants whose mothers have pernicious anemia.