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 drugs.
Taking very high daily doses of vitamin D—for example, 60 to 100 or more times the recommended daily 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 osteodystrophy. Vitamin D has not been proven to prevent leukemia and breast, prostate, colon, or other cancers. Vitamin D supplementation does not effectively treat or prevent depression or cardiovascular disease, nor does it prevent fractures or falls. Some evidence, however, suggests that taking the combined recommended daily allowance of both vitamin D and calcium reduces the risk of hip fractures in those at higher risk.
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.
Treatment of vitamin D toxicity involves stopping vitamin D supplements to offset the effects of a high calcium level in the blood. Fluids are given intravenously as needed.
Drugs, such as corticosteroids or bisphosphonates, are given to suppress the release of calcium from the bones.