Vitamin B12 requirements vary depending on age and pregnancy/breastfeeding status. Infants require 0.4 mcg/day (0-6 months) and 0.5 mcg/day (7-12 months). The recommended dietary allowance for children is 0.9 mcg/day (1-3 years), 1.2 mcg/day (4-8 years), and 1.8 mcg/day (9-13 years). Adults require 2.4 mcg/day, except for 2.6 mcg/day during pregnancy and 2.8 mcg/day while breastfeeding.