Vitamin B12 is a normal component of human milk.[1] The recommended daily intake in lactating women is 2.8 mcg and for infants aged 6 months or less is 0.4 mcg.[2] Lactating mothers may need to supplement their diet to achieve the recommended daily intake or to correct a known deficiency. Low doses of vitamin B12 found in B complex or prenatal vitamins increase milk levels only slightly. Higher daily doses of 50 to 100 mcg or more are needed in cases of maternal deficiency. The breastfed infant is not exposed to excessive vitamin B12 in such cases, and their vitamin B12 status should improve if it was previously inadequate. Poor health outcomes in infants with vitamin B12 deficiency include anemia, abnormal skin and hair development, convulsions, failure to thrive, mental developmental delay, and possibly abnormal movements.[3] One well-recognized at risk group are exclusively breastfed infants of mothers with B12 deficiency due to minimal or no dietary intake of animal products[4-11] or pernicious anemia caused by a maternal malabsorption of B12.[12] Infant vitamin B12 status can be improved through maternal B12 supplementation during pregnancy and lactation.[13-16] Deficient mothers who miss the opportunity to supplement during pregnancy should still be encouraged to supplement during early lactation since infant vitamin B12 status correlates with milk vitamin B12 levels in breastfed infants up to 6 months of age.[17-20] Although there are cases reported of exclusively breastfed infants with vitamin B12 deficiency having biochemical and clinical improvement through adequate maternal supplementation alone,[4] direct supplementation of the infant is recommended when such treatments are available.[9,21,22] Flash heat pasteurization of breastmilk does not reduce milk vitamin B12 concentration.[23]