Vitamin D is a fat-soluble vitamin, which means your body can store reserves of vitamin D in its fat tissues. Sunlight exposure triggers the manufacture of vitamin D, which also is available in multivitamin and standalone supplements, fortified milk and dairy products, fortified cereals, eggs, saltwater fish, mushrooms, vegetable oil, shellfish and sweet potatoes. The normal recommended dose of vitamin D varies by age.
The recommended daily pediatric intake of vitamin D is 5 micrograms or 200 IU, according to the University of Maryland Medical Center, or UMMC. This dosage is appropriate for infants, children and adolescents up to 18 years of age. However, breastfeeding infants who do not yet consume 1 liter of whole milk or dairy-based formula daily should take 10 micrograms or 400 IU of vitamin D per day. Children and adolescents who do not consume at least 1 liter of milk per day should also take a daily vitamin D dose of 10 micrograms or 400 IU.
The recommended daily dosage of vitamin D is 5 micrograms or 200 IU for adults up to age 50, including pregnant and breastfeeding women, according to the UMMC. Vitamin D requirements for older adults are higher; the recommended daily intake is 10 micrograms or 400 IU for adults ages 51 to 70, and 15 micrograms or 600 IU for adults over age 70.
Vitamin D is necessary for the absorption and use of calcium for maintaining bone strength and density; it is particularly important for bone development in children and adolescents, says Phyllis Balch, author of "Prescription for Nutritional Healing." This vitamin also helps regulate heart rhythm and muscle function. Vitamin D deficiency can lead to osteoporosis, poor growth and increased risk of heart disease.
Vitamin D is considered safe in daily doses of up to 25 micrograms or 1,000 IU for children under age 12, and up to 50 micrograms or 2,000 IU for adolescents and adults, according to the UMMC. Exceeding these limits may cause side effects such as itching, constipation, vomiting, loss of appetite, bone pain and fatigue. Talk to your physician before using calcium supplements or exceeding the recommended daily intake, especially if you suffer from heart disease, hypercalcemia or kidney disease.