The ideal vitamin D blood level is 45–60 ng/mL. To reach those levels, follow these guidelines.

Infants and children 12 and younger: 400–1,000 IU daily

Teens age 13–18: 1,000 IU daily

Adults in good health: 2,000–5,000 IU daily

Adults with health problems: 2,000–10,000 IU daily. Obese adults or those on certain medications, such as ketoconazole (an antifungal), may require two to three times more.