The standard dose of vitamin B-12 depends on the age and circumstance of the person and varies between 1 and 25 micrograms per day, reports WebMD. Much higher doses have been used in scientific studies on vitamin B-12 deficiency, says Mayo Clinic.
Daily doses of vitamin B-12 are 0.4 mcg for infants aged 0 to 6 months, 0.5 mcg for infants 7 to 12 months, 0.9 mcg for children 1 to 3 years, 1.2 mcg for children 4 to 8 years, 1.8 mcg for children 9 to 13 years, 2.4 mcg for adolescents and adults, 2.6 mcg for pregnant women and 2.8 mcg for breastfeeding women, as stated by WebMD.
Doses ranging from 125 to 2,000 mcg have been used to treat vitamin B-12 deficiency, according to MedlinePlus. Intravenous doses of 5 to 20 grams of vitamin B-12 have been used in cases of cyanide poisoning, reports Mayo Clinic.