Poor health outcomes in infants with vitamin B 12 deficiency include anemia, abnormal skin and hair development, convulsions, weak muscle tone, failure to thrive, mental developmental delay, and potentially abnormal movements.[4-8] Well-recognized at risk groups are exclusively breastfed infants of mothers with B 12 deficiency due to minimal or no dietary intake of animal products[9-21] or pernicious anemia caused by a maternal malabsorption of B 12 .[18,22] Infant vitamin B 12 status can be improved through maternal B 12 supplementation during pregnancy and lactation.[23-26] Deficient mothers who miss the opportunity to supplement during pregnancy should still be encouraged to supplement during early lactation since infant vitamin B 12 status correlates with milk vitamin B 12 levels in breastfed infants up to 6 months of age.[27-30] Although there are cases reported of exclusively breastfed infants with vitamin B 12 deficiency having biochemical and clinical improvement through adequate maternal supplementation alone,[9] direct supplementation of the infant is recommended when such treatments are available.[31-33] Drug Levels Methylcobalamin is the major form of vitamin B 12 in milk
A: Side effects are rare and mildsome may experience slight bruising at the injection site or a metallic taste
"Pernicious Anemia", StatPearls , Treasure Island (FL): StatPearls Publishing, PMID 31082033, retrieved July 15, 2025 "Vitamin B12 or folate deficiency anaemia Diagnosis"
Either way, the following tips can give you some control over the process and make self-injections less stressful
