It is well known that vitamin D is one of the most important substances for the body to maintain growth and development, and since the body cannot synthesize it or has limited ability to do so, it is often necessary to increase the intake of vitamin D. Both infants and adults should ensure that they have the right amount of intake every day. Infants and young children are growing vigorously and their bones are developing rapidly, so they need adequate amounts of vitamin D to maintain normal bone development, but the more vitamin D they get, the better. The daily dose of vitamin D should be 400 IU for infants less than one year old, 600 IU for toddlers, children, and adults <70 years old, and 800 IU for elderly people >70 years old.