Vitamin D is a fat-soluble vitamin that can be obtained from the diet or synthesized by the skin following exposure to direct sunlight. Cholecalciferol, or D3, and ergocalciferol, or D2, are two of the most common forms of vitamin D supplements. The potency of cholecalciferol is higher when compared to ergocalciferol with higher doses of cholecalciferol rarely exceeding 5,000 international units, or IU, per day. On the other hand, ergocalciferol is available by prescription as capsules or softgels that contain 50,000 international units. High dose ergocalciferol is often used on a temporary basis to replace vitamin D stores in patients with deficiency and although generally safe, side effects and serious adverse reactions can occur.

Allergy

Although rare, some patients may experience an allergic reaction to vitamin D supplements. Ergocalciferol 50,000 IU capsules often include additives and dyes that may trigger an allergic reaction in a small portion of the population. Serious allergic reactions including hives, swelling of the lips, dizziness or difficulty breathing will require immediate medical attention.

Hypercalcemia

Since the primary role of vitamin D is to regulate the absorption of dietary calcium into the bloodstream, supplementation with any vitamin D products can cause excessively high levels of calcium. Hypercalcemia has been associated with cardiovascular implications as well as the formation of kidney stones. Hypercalcemia is a serious condition and patients taking vitamin D supplements should have routine monitoring of calcium and vitamin D in the blood.

Effects on Pregnancy and Nursing

Vitamin D is an important component of the diet and is required for a healthy body even during times of pregnancy or breastfeeding. However, supplementation with ergocalciferol 50,000 IU can lead to excess vitamin D and should be avoided. According to the ergocalciferol, or Drisdol TM, product package insert, hypervitaminosis D has been found to cause fetal abnormalities in animals. Ergocalciferol 50,000 IU is currently rated a pregnancy category C, which means that insufficient data exists on the effects towards human fetuses but adverse effects have been seen in animal studies. In addition, there was a reported case of hypercalcemia in a nursing infant whose mother was given large doses of vitamin D, reported by LD Goldberg in a study published by "Lancet" in December, 1972.

Hypervitaminosis D

Vitamin D toxicity, otherwise known as Hypervitaminosis D, can lead to kidney impairment, calcification of renal tissue and formation of kidney stones. In addition, toxicity can also lead to cognitive impairment. Patients using prescription high dose supplementation with ergocalciferol often have blood levels of vitamin D routinely checked by their physicians. Patients should also always let their physician know if they plan on taking over-the-counter vitamin D supplements.