What is the safe dosage amount for vitamin D3?

The maximum safe daily dosage of vitamin D is 2500 IU for ages 1 to 3; 3000 IU for ages 4 to 8; and 4000 IU for others, says the National Academies. The National Academies also says that most Americans need no more than 600 IU daily to maintain health.

Excess vitamin D carries a risk of excess calcium in the blood, and that excess calcium can produce health risks including constipation, nausea, mental confusion, heart rhythm abnormalities and kidney stones, according to WebMD. However, too little vitamin D has a risk of deficiency diseases, such as Rickets and osteomalacia, according to the National Institutes of Health.