Vitamin D functions as both a vitamin and a hormone. Your body can manufacture it from sunlight or get it through a diet containing fortified foods. In some instances, however, you might require supplementation such as living in an area with little sunlight or the use of certain medications. Supplementing can also help prevent and treat osteoporosis though other purported uses for vitamin D supplements remain unproven, according to the Beth Israel Deaconess Medical Center. Supplements come in two forms: vitamin D-2 and vitamin D-3. Like drugs, natural supplements can carry the risk of adverse effects if used in excess or in inappropriate circumstances and vitamin D is no exception. Work with your doctor, who can monitor your treatment and perform periodic blood testing to track your levels of the vitamin.
Medication Interactions
Using vitamin D supplements at the same time as medications that increase levels of the vitamin in your body can increase the risk of adverse effects. Medications include oral contraceptives, isoniazid and thiazide. They might also interfere with the actions of calcium-channel blockers and atorvastatin and increase the risk of toxic side effects of digoxin.
Adverse Reactions
Adverse reactions associated with excess vitamin D intake include excess calcium levels that can damage the heart, blood vessels and kidneys, and cause weight loss, excessive urination, excessive thirst, metallic taste, bone pain, fatigue, itching, vomiting, diarrhea, constipation, sore eyes and abnormal heart beat. The National Institutes of Health Office of Dietary Supplements reports research that found the use of calcium and vitamin D supplements in post-menopausal women increased the risk of kidney stones 17 percent.
Potentially Contraindicated Uses
If you have certain medical conditions, you might not be able to use vitamin D supplements at all, including those that affect the heart or kidney or that raise blood levels of phosphorus or calcium. Your doctor can determine the appropriateness of using supplements in these instances.
Dosage Guidelines
Staying within the suggested dosage range can minimize adverse effects. The typical daily dosages include 600 IU of vitamin D daily for individuals under age 70, and 800 IU for people 71 years and older. Pregnant and lactating women should take 600 IU. The NIH lists 4,000 IU as the daily upper intake level, though you should definitely not take more than the standard daily dose unless your doctor has suggested it.
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