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Pronunciations cholecalciferol corticosteroid ergocalciferol hypercalcemia hyperparathyroidism osteoma osteomalacia osteoporosis rifampin

Two forms of vitamin D Some Trade Names
See Ergocalciferol
are important for nutrition:

• Vitamin D₂ (ergocalciferol): This form is synthesized from plants and yeast precursors. It is also the form used in very high dose supplements.
• Vitamin D₃ (cholecalciferol): This form is the most active form of vitamin D Some Trade Names
  See Ergocalciferol
  . It is formed in the skin when the skin is exposed to direct sunlight. The most common food source is fortified foods, mainly cereals and dairy products. Vitamin D Some Trade Names
  See Ergocalciferol
  ₃ is also present in fish liver oils and fatty fish. Human breast milk contains only small amounts of vitamin D Some Trade Names
  See Ergocalciferol
  .

Vitamin D Some Trade Names
See Ergocalciferol
is stored mainly in the liver. Vitamin D Some Trade Names
See Ergocalciferol
₂ and D₃ are not active in the body. Both forms must be processed (metabolized) by the liver and kidneys into an active form called calcitriol Some Trade Names
ROCALTROL
. This active form promotes absorption of calcium and phosphorus from the intestine. Calcium and phosphorus, which are minerals, are incorporated into bones to make them strong and dense (a process called mineralization). Thus, vitamin D Some Trade Names
See Ergocalciferol
is necessary for the formation, growth, and repair of bones. Vitamin D Some Trade Names
See Ergocalciferol
also enhances immune function and improves muscle strength. Requirements for vitamin D Some Trade Names
See Ergocalciferol
increase as people age.

Vitamin D Deficiency

• The most common cause is lack of exposure to sunlight, but certain disorders can also cause the deficiency.
• Without enough vitamin D Some Trade Names
  See Ergocalciferol
  , muscle and bone weakness and pain occur.
• Infants develop rickets: The skull is soft, bones grow abnormally, and infants are slow to sit and crawl.
• Blood tests and sometimes x-rays are done to confirm the diagnosis.
• From birth, breastfed infants should be given vitamin D Some Trade Names
  See Ergocalciferol
  supplements because breast milk contains little vitamin D Some Trade Names
  See Ergocalciferol
  .
• Vitamin D Some Trade Names
  See Ergocalciferol
  supplements taken by mouth or given by injection usually results in a complete recovery.

Vitamin D Some Trade Names
See Ergocalciferol
deficiency is common. Most commonly, it occurs when the skin is not exposed to enough sunlight. Almost no one consumes enough vitamin D Some Trade Names
See Ergocalciferol
from foods to prevent vitamin D Some Trade Names
See Ergocalciferol
deficiency when exposure to sunlight is inadequate.

In vitamin D Some Trade Names
See Ergocalciferol
deficiency, calcium and phosphate levels in the blood decrease because vitamin D Some Trade Names
See Ergocalciferol
is necessary for absorption of these minerals. Because not enough calcium and phosphate are available to maintain healthy bones, vitamin D Some Trade Names
See Ergocalciferol
deficiency may result in a bone disorder called rickets in children or osteomalacia in adults. In a pregnant woman, vitamin D Some Trade Names
See Ergocalciferol
deficiency causes the deficiency in the fetus, and the newborn has a high risk of rickets. Occasionally, the deficiency is severe enough to cause osteomalacia in the woman. Vitamin D Some Trade Names
See Ergocalciferol
deficiency makes osteoporosis worse. To try to increase the low calcium level in blood caused by vitamin D Some Trade Names
See Ergocalciferol
deficiency, the body may produce more parathyroid hormone. However, as the parathyroid hormone level becomes high (a condition called hyperparathyroidism), the hormone draws calcium out of bone to increase the calcium level in blood. Thus, bones are weakened.

Did You Know... Lack of exposure to sunlight can cause vitamin D Some Trade Names See Ergocalciferol deficiency. Most older people need vitamin D Some Trade Names See Ergocalciferol supplements.

Causes

The most common cause is inadequate exposure to sunlight. Thus, vitamin D Some Trade Names
See Ergocalciferol
deficiency occurs mainly among people who do not spend much time outdoors: older people and people who live in an institution such as a nursing home. The deficiency can also occur in the winter at northern and southern latitudes or in people who keep their bodies covered, such as Muslim women. Because breast milk contains only small amounts of vitamin D Some Trade Names
See Ergocalciferol
, breastfed infants who are not exposed to enough sunlight are at risk of the deficiency and rickets.

When the skin is exposed to enough sunlight, the body usually forms enough vitamin D Some Trade Names
See Ergocalciferol
. However, certain circumstances increase the risk of vitamin D Some Trade Names
See Ergocalciferol
deficiency even when there is exposure to sunlight:

• The skin forms less vitamin D Some Trade Names
  See Ergocalciferol
  in response to sunlight in certain groups of people. They include people with darker skin (particularly blacks), older people, and people who use sunscreen.
• The body may not be able to absorb enough vitamin D Some Trade Names
  See Ergocalciferol
  from foods. In malabsorption disorders, people cannot absorb fats normally (see Malabsorption). They also cannot absorb vitamin D Some Trade Names
  See Ergocalciferol
  because it is a fat-soluble vitamin, which is normally absorbed with fats in the small intestine.
• The body may not be able to convert vitamin D Some Trade Names
  See Ergocalciferol
  to an active form. Certain kidney and liver disorders and several rare hereditary disorders interfere with this conversion, as do certain drugs, such as some anticonvulsants and rifampin Some Trade Names
  RIFADINRIMACTANE
  .

Spotlight on Aging Older people are likely to develop vitamin D Some Trade Names See Ergocalciferol deficiency for several reasons: Their requirements are higher than younger persons. They tend to spend less time outdoors, or stay indoors more in the winter, and thus are not exposed to enough sunlight. They may not be exposed to enough sunlight because they are housebound, live in long-term care facilities, or need to stay in the hospital for a long time. When exposed to sunlight, their skin does not form as much vitamin D Some Trade Names See Ergocalciferol . They consume so little vitamin D Some Trade Names See Ergocalciferol in their diet that even taking vitamin D Some Trade Names See Ergocalciferol supplements in low doses (such as 400 units per day) does not prevent the deficiency. They may have disorders or take drugs that interfere with the processing of vitamin D Some Trade Names See Ergocalciferol . New studies suggest that older adults may need more vitamin D Some Trade Names See Ergocalciferol than the current recommended dietary allowance or even the recommended upper limits. In fact, they may need 1000 to 2000 IU (or more) daily, but taking such high amounts should be done only after consulting a doctor. Older people who take high amounts of vitamin D Some Trade Names See Ergocalciferol supplements need to have periodic blood tests to check their levels of calcium, vitamin D Some Trade Names See Ergocalciferol , and parathyroid hormone.

Symptoms

Vitamin D Some Trade Names
See Ergocalciferol
deficiency can cause muscle aches, weakness, and bone pain in people of all ages. Muscle spasms, which are caused by a low calcium level, may be the first sign of rickets in infants.

In young infants who have rickets, the entire skull may be soft. Older infants may be slow to sit and crawl, and the spaces between the skull bones (fontanelles) may be slow to close. In children aged 1 to 4 years, bone growth may be abnormal, causing an abnormal curve in the spine and bowlegs or knock-knees. These children may be slow to walk. For older children and adolescents, walking is painful. The pelvic bones may flatten, narrowing the birth canal in adolescent girls. In adults, the bones, particularly the spine, pelvis, and leg bones, weaken. Affected areas may be painful to touch, and fractures may occur.

In older people, bone fractures may result from only slight jarring or a minor fall.

Diagnosis

Doctors suspect vitamin D Some Trade Names
See Ergocalciferol
deficiency when people report an inadequate diet or exposure to sunlight. Doctors also suspect the deficiency in older adults, especially in those with decreased bone density (for example, with osteoporosis) or broken bones. Blood tests to measure vitamin D Some Trade Names
See Ergocalciferol
can confirm the deficiency. X-rays may also be taken. The diagnosis of rickets or osteomalacia is based on symptoms, the characteristic appearance of bones on x-rays, and a low level of vitamin D Some Trade Names
See Ergocalciferol
in the blood.

Prevention and Treatment

Many people need to take vitamin D Some Trade Names
See Ergocalciferol
supplements. Getting enough exposure to sunlight may be difficult, especially because the skin also needs to be protected from sun damage. The diet rarely contains enough vitamin D Some Trade Names
See Ergocalciferol
to compensate for lack of sunlight. Many multiple vitamins contain little or no vitamin D Some Trade Names
See Ergocalciferol
, so most people need to take vitamin D Some Trade Names
See Ergocalciferol
supplements. These supplements are particularly important for people who are at risk (such as people who are older, housebound, or living in long-term care facilities). Commercially available liquid milk (but not cheese or yogurt) is fortified in the United States and Canada. Many other countries do not fortify milk with vitamin D Some Trade Names
See Ergocalciferol
. Breakfast cereals may also be fortified.

In breastfed infants, starting vitamin D Some Trade Names
See Ergocalciferol
supplements at birth is particularly important because breast milk contains little vitamin D Some Trade Names
See Ergocalciferol
. Commercial infant formulas contain enough vitamin D Some Trade Names
See Ergocalciferol
.

Treatment involves taking high doses of vitamin D Some Trade Names
See Ergocalciferol
by mouth or by injection daily or weekly for 1 to 2 months or longer. If muscle spasms are present or calcium is thought to be deficient, calcium supplements are also given. If phosphate is deficient, phosphate supplements are given. Usually, this treatment leads to a complete recovery. People with a chronic liver or kidney disorder may require special formulations of vitamin D Some Trade Names
See Ergocalciferol
supplements.

Vitamin D Excess

Taking very high daily doses of vitamin D Some Trade Names
See Ergocalciferol
—for example, 50 or more times the recommended daily allowance (RDA)—over several months can cause toxicity and a high calcium level in the blood (hypercalcemia—see Minerals and Electrolytes: Hypercalcemia).

Early symptoms are loss of appetite, nausea, and vomiting, followed by excessive thirst, weakness, nervousness, and high blood pressure. Because the calcium level is high, calcium may be deposited throughout the body, particularly in the kidneys, blood vessels, lungs, and heart. The kidneys may be permanently damaged and malfunction, resulting in kidney failure.

Vitamin D Some Trade Names
See Ergocalciferol
excess is usually diagnosed when blood tests detect a high calcium level in a person who takes high doses of vitamin D Some Trade Names
See Ergocalciferol
. The diagnosis is confirmed by measuring the level of vitamin D Some Trade Names
See Ergocalciferol
in the blood.

Treatment consists of the following:

• Stopping vitamin D Some Trade Names
  See Ergocalciferol
  supplements
• Following a low-calcium diet for a while to offset the effects of a high calcium level in the body
• Taking drugs (such as corticosteroids or bisphosphonates) to suppress the release of calcium from the bones

Last full review/revision August 2007 by Larry E. Johnson, MD, PhD