Ergocalciferol is vitamin D2. Vitamin D is important for the absorption of calcium from the stomach and for the functioning of calcium in the body.

Ergocalciferol is used to treat hypoparathyroidism (decreased functioning of the parathyroid glands).

Ergocalciferol is also used to treat rickets (softening of the bones caused by vitamin D deficiency) or low levels of phosphate in the blood (hypophosphatemia).

Ergocalciferol may also be used for purposes not listed in this medication guide.

Do not use this medication if you have ever had an allergic reaction to vitamin D, or if you have high levels of calcium or vitamin D in your blood, or if you have any condition that makes it hard for your body to absorb nutrients from food (malabsorption).

Before you take this medication, tell your doctor if you are allergic to any drugs or dyes, or if you have heart disease, coronary artery disease, kidney disease, or an electrolyte imbalance.

Do not take other vitamin or mineral supplements unless your doctor has told you to.

Avoid using calcium supplements or antacids without your doctor's advice. Use only the specific type of supplement or antacid your doctor recommends. Tell your doctor about all medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor.

Seek emergency medical attention if you think you have used too much of this medicine. An overdose of vitamin D can cause serious or life-threatening side effects.

Overdose symptoms may include headache, weakness, drowsiness, dry mouth, nausea, vomiting, constipation, muscle or bone pain, metallic taste in the mouth, weight loss, itchy skin, changes in heart rate, loss of interest in sex, confusion, unusual thoughts or behavior, feeling unusually hot, severe pain in your upper stomach spreading to your back, or fainting.

Do not use this medication if you have ever had an allergic reaction to vitamin D, or if you have:

• high levels of calcium in your blood (hypercalcemia);

• high levels of vitamin D in your body (hypervitaminosis D); or

• any condition that makes it hard for your body to absorb nutrients from food (malabsorption).

To make sure you can safely take ergocalciferol, tell your doctor if you have any of these other conditions:

• heart disease;

• coronary artery disease;

• kidney disease; or

• an electrolyte imbalance.

FDA pregnancy category C. It is not known whether ergocalciferol will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medication.

Ergocalciferol can pass into breast milk and may harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.