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Vitamin D 25-Dihydroxy (Calcitriol) Test

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About Our Vitamin D 25-Dihydroxy (Calcitriol) Test

Note: Fasting is not required for this test.

Typically, Vitamin D's most common subcategories are Vitamin D2 and D3; Vitamin D2 comes from digesting vitamin D from plant and fungal food sources, and vitamin D3 is absorbed via the skin when it takes in sunlight.

This Vitamin D 25-Dihydroxy (Calcitriol) Test measures the bioactive form of vitamin D, and can help diagnose conditions that cause excessive vitamin D production. It is also used in the differential diagnosis of hypocalcemia (low calcium levels) and to monitor patients with renal osteodystrophy or chronic kidney failure.

This test is not suitable for diagnosis of vitamin D deficiency and monitoring supplementation in most individuals. Our Vitamin D 25-Hydroxy (Calcidiol) Test is the recommended test for monitoring vitamin D levels for deficiency.


The Vitamin D, 25-Dihydroxy Test is used to help diagnose or monitor the following conditions:

  • Sarcoidosis
  • Hypocalcemia and hypercalcemia
  • Kidney (renal) disease or failure
  • Parathyroid disorder
  • Certain cases of lymphoma

This vitamin D 25-dihydroxy test is also sometimes ordered when vitamin D, calcium, phosphorus, and/or magnesium supplementation is prescribed. Low levels of vitamin D 25-dihydroxy can be seen in kidney disease cases. Low calcitriol levels is one of the earliest changes to occur in persons with early kidney failure.

A high level of vitamin D 25-dihydroxy may occur when there is excess parathryoid hormone or when there are diseases, such as sarcoidosis or some lymphomas, that can make calcitriol outside of the kidneys.


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