What is calcitriol, and how does it work (mechanism of action)?

Calcitriol is a synthetic (man-made) active form of vitamin D3 (cholecalciferol). It is used to treat and prevent low levels of calcium in the blood of patients who have kidney disease or problems with their parathyroid gland, the gland that controls the amount of calcium in blood through its secretion of parathyroid hormone.

Calcium plays an important role in maintaining bone health, and low levels of calcium may cause bone disease. Calcitriol increases blood levels of calcium by increasing the absorption of calcium in the kidneys, increasing the absorption of calcium and phosphorus from the intestine, and increasing the release of calcium and phosphorus from the bones. Calcitriol helps the body to use calcium found in foods and supplements.

What brand names are available for calcitriol?


Is calcitriol available as a generic drug?


Do I need a prescription for calcitriol?


What are the side effects of calcitriol?


Excessive vitamin D may lead to hypercalcemia (abnormally high levels of calcium in the blood), hypercalciuria (elevated levels of calcium in the urine), hyperphosphatemia (high levels of phosphate in the blood), and bone disease. To avoid complications, vitamin D and its derivatives should be avoided during calcitriol therapy.

Hypercalcemia has been reported in patients treated with calcitriol. Patients should avoid making any sudden changes in their dietary calcium intake and maintain adequate intake of fluid (hydration) during treatment.

Which drugs or supplements interact with calcitriol?

Calcitriol should not be used with other vitamin D products because of the increased risk of additive side effects and toxicity.

Cholestyramine (Questran), colestipol (Colestid), mineral oil, and orlistat (Alli, Xenical) may decrease the intestinal absorption of calcitriol. Separating the administration of these medications and calcitriol may prevent this interaction.

Phenytoin (Dilantin) and phenobarbital (Luminal) may reduce blood concentrations of calcitriol, decreasing treatment effectiveness. Higher doses of calcitriol may be necessary if these drugs are used together with calcitriol.

Thiazide diuretics may increase the blood levels of calcium. Since calcitriol also increases calcium levels, taking these two types of medications together may cause hypercalcemia (abnormally highly levels of calcium).

Calcitriol should be used cautiously in patients taking digoxin (Lanoxin). High levels of calcium may cause symptoms of digoxin toxicity such as irregular heartbeats.

Ketoconazole (Nizoral) may decrease the activity of enzymes responsible for metabolizing or breaking down calcitriol and lead to the side effects of excessive vitamin D.

Magnesium containing medications (for example, antacids) should be avoided in patients undergoing chronic renal dialysis who are taking calcitriol. These patients are at high risk of experiencing hypermagnesemia (high blood levels of magnesium) as their kidneys are unable to remove adequate amounts of magnesium from the blood.

What is the dosage for calcitriol?

  • The recommended initial oral dose for treating low calcium due to kidney dialysis is 0.25 mcg daily.
  • The dose may be increased by 0.25 mcg daily every 4 to 8 weeks.
  • Most patients respond to 0.5 to 1 mcg daily.
  • The oral dose for treating hypoparathyroidism is 0.25 mcg to 2 mcg daily.

Is calcitriol safe to take if I’m pregnant or breastfeeding?

There are no adequate and well-controlled studies of calcitriol treatment in pregnant women. Calcitriol should be used during pregnancy only if the potential benefit justifies the potential risk to the unborn baby.

Calcitriol may be excreted in human milk. Mothers should not breastfeed while taking calcitriol.

What else should I know about calcitriol?

What preparations of calcitriol are available?
  • Oral liquid filled capsules: 0.25 and 0.5 mcg
  • Oral solution: 1 mcg/ml
  • Solution for injection: 1 and 2 mcg/ml
How should I keep calcitriol stored?

Calcitriol should be stored at room temperature, between 15 C and 30 C (59 F and 86 F). Protect from light.

Medically Reviewed on 3/15/2019


Medically reviewed by John P. Cunha, DO, FACOEP; Board Certified Emergency Medicine


FDA Prescribing Information