For vitamin C, infants age 0 to 6 months need 40 milligrams a day, while infants 7 to 12 months need 50 milligrams a day. Children ages 1 to 3 years need 15 milligrams daily, those aged 4 to 8 need 25 milligrams daily, and children age 9 to 13 need 45 milligrams daily.