Taking very high doses of vitamin D supplements can cause vitamin D toxicity.
Vitamin D toxicity causes high levels of calcium in the blood.
People with vitamin D toxicity may lose their appetite, feel nauseated, vomit, and feel weak and nervous.
Doctors diagnose the toxicity by measuring levels of calcium and vitamin D in the blood.
Treatment involves stopping vitamin D supplements and giving the person fluids and sometimes medications.
(See also Overview of Vitamins.)
Taking very high daily doses of vitamin D—for example, 60 to 100 or more times the recommended dietary allowance (RDA)—over several months can cause toxicity and a high calcium level in the blood (hypercalcemia). Levels of calcium become high because when levels of vitamin D are high, the following occur:
More bone is broken down than is reformed. (Normally, bones are continuously broken down and reformed—in a process called remodeling—to adjust to the changing demands placed on them.) As a result, calcium is released from the bone into the bloodstream.
More calcium is absorbed from food in the intestine.
Vitamin D may be used to treat psoriasis, hypoparathyroidism, and renal osteodystrophyvitamin D deficient, especially those who are institutionalized. However, large doses of vitamin D may increase fracture risk.
Symptoms of Vitamin D Excess
Early symptoms of vitamin D toxicity are loss of appetite, nausea, and vomiting, followed by 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.
Diagnosis of Vitamin D Excess
Blood tests
Vitamin D excess is usually diagnosed when blood tests detect a high calcium level in a person who takes high doses of vitamin D. Doctors also measure the level of vitamin D in the blood.
Treatment of Vitamin D Excess
Fluids given intravenously
Medications
Treatment of vitamin D
Medications, such as corticosteroids or bisphosphonates, are given to suppress the release of calcium from the bones.
