Vitamin D is an essential vitamin required by a variety of organs in the body, particularly the bones. Vitamin D plays a key role in regulating several minerals in the body, including calcium and phosphorus, which are involved in building and maintaining healthy bones. Although vitamin D is generally safe and well tolerated, it may cause side effects. In very large doses, vitamin D can cause symptoms of toxicity. As with any health supplement, you should consult your doctor before taking vitamin D supplements.
High Calcium Levels
Taking large doses of vitamin D for long periods of time can cause high levels of calcium to accumulate in the blood. Vitamin D regulates how much calcium is absorbed by the body from food, and excessively high levels of vitamin D cause the body to absorb too much calcium. High levels of calcium in the blood can lead to calcification, or hardening, of the blood vessels, a condition known as atherosclerosis, which can cause heart disease. High levels of calcium can also lead to calcification of the heart and other organs, causing damage to these organs. The risk of kidney stones also increases with elevated blood calcium levels.
Additional Symptoms
Several general symptoms can also result from an overdose of vitamin D, including nausea, vomiting, loss of appetite, anorexia and unintended weight loss. Fatigue, muscle weakness and excess sleepiness have also been reported. Additional symptoms may include headache, dry mouth and an unusual metallic taste in the mouth.
Disease Interactions
The effects of a vitamin D overdose can be exacerbated by many existing diseases. Patients with kidney disease have a reduced ability to filter calcium from the blood, so elevations in blood calcium levels are more likely to occur. Several other diseases, including lymphoma, hyperparathyroidism, sarcoidosis and histoplasmosis, also may increase the effects of vitamin D on blood calcium levels and worsen disease symptoms. Vitamin D toxicity can also worsen existing cases of atherosclerosis.
Dosage
The U.S. Institute of Medicine has set a tolerable upper intake level of 4,000 international units, abbreviated IU, per day for vitamin D. However, there is disagreement among health professionals on whether this level is too high or too low. Some doctors think doses of more than 2,000 IU increase the risk of toxicity symptoms, reports MedlinePlus. Other doctors think doses up to 10,000 IU can be given safely, according to the Linus Pauling Institute at Oregon State University. You should consult your doctor to determine the right dose of vitamin D for your health needs.
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