Many breakfast cereals are fortified with B12, ranging from 0.6 mcg (25% RDA) to 2.4 mcg (100% RDA). They provide a variety of vitamins and minerals, including vitamins A, C, D, and other B ...

No upper limit has been set for vitamin B12, as there is no toxic level. However, a recent study in the journal JAMA Network ...

800 IU (20 mcg) per day increases vitamin D blood levels 8 ng/ml (20 nmol/L). 1000 IU (25 mcg) per day increases vitamin D blood levels 10 ng/ml (25 nmol/L). 2000 IU (50 mcg) per day increases ...