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Vitamin D 1,25 Dihydroxy

Endocrine & Reproductive

1,25(OH)2DCalcitriol

Review status

Currently under review

Pending specialist review and validation.

What it shows

This test measures 1,25-dihydroxyvitamin D, also called calcitriol, the active hormone form of vitamin D. Calcitriol helps your intestines absorb calcium and phosphate and works with parathyroid hormone to keep bones and muscles functioning properly.

Your body makes calcitriol mainly in the kidneys from 25-hydroxyvitamin D, the storage form made in the liver. Levels are tightly regulated by kidney function, parathyroid hormone, calcium, and phosphate, and can also be influenced by certain illnesses and medications.

Why it matters

Clinicians order this test when they suspect problems with calcium balance that may be related to kidney disease, parathyroid disorders, or conditions that can produce calcitriol outside the kidneys, such as some granulomatous diseases. It may also be used when calcium levels are high or low for unclear reasons, or to monitor therapy with calcitriol or related medicines.

This test is not the usual way to assess overall vitamin D stores; that is done with a 25-hydroxyvitamin D test. Measuring calcitriol helps pinpoint why calcium or phosphate is out of balance and guides treatment decisions in specific clinical situations.

Understanding your results

Your result is interpreted in the context of your symptoms, calcium and phosphate levels, parathyroid hormone, kidney function, and the medications you take. A value outside your laboratory’s reference interval does not always mean there is a disease, and a result within the interval may still need follow-up if you have ongoing symptoms or risk factors.

If your value is unexpected, your clinician may repeat the test, review your medications and supplements, and order related tests such as 25-hydroxyvitamin D, parathyroid hormone, calcium, phosphate, and kidney function. Do not change supplements or prescribed medications without discussing the plan with your care team.

Reference ranges

90 – 174 pmol/L
All sexes
0 days – 150 years

Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.

Factors that could impact Vitamin D 1,25 Dihydroxy

  • Kidney function

    Most calcitriol is produced in the kidneys. Reduced kidney function can lower calcitriol regardless of your vitamin D intake, while recovery or treatment can change levels over time.

  • Parathyroid hormone (PTH)

    PTH stimulates the kidney enzyme that makes calcitriol. High PTH can raise calcitriol, while low PTH can reduce it, affecting calcium and phosphate balance.

  • Granulomatous disease

    Conditions like sarcoidosis or tuberculosis can produce calcitriol outside the kidneys, sometimes leading to elevated levels and high calcium despite normal kidney function.

  • Medications and supplements

    Calcitriol or analogs, high-dose vitamin D, and some drugs such as anticonvulsants, glucocorticoids, ketoconazole, or rifampin can alter calcitriol synthesis or metabolism.

  • Calcium and phosphate intake

    Dietary calcium and phosphate influence regulatory hormones that in turn affect calcitriol production. Extreme intakes or binders may shift levels.

  • Pregnancy

    Calcitriol often increases during pregnancy due to physiologic changes that support fetal bone development, which can affect interpretation.

  • Timing and consistency of testing

    Although strict fasting is not usually required, using the same laboratory and similar timing for repeat tests helps reduce variation and aids comparison.

  • Underlying vitamin D stores

    Low 25-hydroxyvitamin D can limit the substrate available to make calcitriol, while sufficient stores support normal hormone production.

2026

References

  1. McGill University Health Centre. (2005, April 17). Vitamin D 1, 25 Dihydroxy (Task CD 699411). Laboratory reference ranges.
  2. Holick, M. F., Binkley, N. C., Bischoff-Ferrari, H. A., Gordon, C. M., Hanley, D. A., Heaney, R. P., Murad, M. H., & Weaver, C. M. (2011). Evaluation, treatment, and prevention of vitamin D deficiency: An Endocrine Society clinical practice guideline. The Journal of Clinical Endocrinology & Metabolism, 96(7), 1911–1930.
  3. Kidney Disease: Improving Global Outcomes (KDIGO) CKD-MBD Update Work Group. (2017). KDIGO 2017 clinical practice guideline update for the diagnosis, evaluation, prevention, and treatment of chronic kidney disease–mineral and bone disorder (CKD-MBD). Kidney International Supplements, 7(1), 1–59.