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Vitamin D (1,25-Dihydroxy)

Measures calcitriol, the active hormone form of vitamin D, to look into calcium, kidney and bone questions rather than to check vitamin D status.

AI-verified against cited sources. Awaiting expert reviewAlso called 1,25(OH)2D, 1,25-(OH)2DLOINC 1649-3

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What it is

Calcitriol is the hormone form of vitamin D. Your liver turns vitamin D into 25-hydroxyvitamin D, and your kidneys then convert a small amount into calcitriol, which helps your gut absorb calcium. Calcitriol is made on demand and lasts only a few hours in the blood, so its level does not show how much vitamin D you have stored. For that, clinicians use the 25-hydroxy vitamin D test.

Why it matters

Clinicians order this test for specific reasons, such as unexplained high calcium, advanced kidney disease, certain bone and mineral disorders in children and adults, or conditions like sarcoidosis that can make extra calcitriol. It is not a routine vitamin D check, and ARUP notes that a normal result does not rule out vitamin D deficiency.

If it’s low

A low level can be a sign that the kidneys are not making enough calcitriol, which is common in chronic kidney disease. It is also low when parathyroid hormone is low. A low result does not mean you lack vitamin D, because your 25-hydroxy vitamin D level can be normal.

Common causes

  • Chronic kidney disease
  • Low parathyroid hormone (hypoparathyroidism)
  • Rare inherited conditions of vitamin D activation
  • Some medicines, such as the antifungal drug ketoconazole

What can help

  • Ask your clinician which related tests, such as calcium, phosphate, parathyroid hormone and 25-hydroxy vitamin D, should be looked at with it
  • Ask whether your kidney function (eGFR) has been checked recently

If it’s high

A high level can be a sign that something is making extra calcitriol or that parathyroid hormone is pushing the kidneys to make more. Taking calcitriol or related prescription vitamin D medicines can raise the result, and pregnancy also raises it. Conditions such as sarcoidosis and tuberculosis can make calcitriol outside the kidneys, which can raise blood calcium.

Common causes

  • Taking prescription calcitriol or a related vitamin D medicine
  • Pregnancy, where a rise is expected
  • High parathyroid hormone activity (hyperparathyroidism)
  • Sarcoidosis and other granulomatous conditions, including tuberculosis
  • Rare inherited conditions that affect vitamin D breakdown, such as CYP24A1 deficiency

What can help

  • Ask your clinician what is driving the result; calcium, parathyroid hormone and 25-hydroxy vitamin D are usually looked at together
  • Share all medicines and supplements you take, including prescription vitamin D forms

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: 19.9–79.3 pg/mL. Source: ARUP Laboratories, Parkview Health Laboratory, Calcified Tissue International.

What can affect your result

  • Parathyroid hormone, calcium and phosphate, which control how much the kidneys make
  • Kidney function: levels are usually low in chronic kidney disease
  • Pregnancy raises levels
  • Age: children's levels are higher than adults'
  • Assay method: immunoassay and LC-MS/MS intervals differ
  • Grossly hemolyzed or lipemic samples are rejected (ARUP).
  • Immunoassays and LC-MS/MS give different results, and there is no standard reference material.
  • Pregnancy raises levels; kidney disease and low parathyroid hormone lower them.
  • Calcitriol or related prescription vitamin D medicines raise the result; the antifungal drug ketoconazole lowers it.

Hours. The half-life is short, about 4-6 hours in one review (Alonso 2022), so the level moves quickly with parathyroid hormone, calcium and phosphate.

When to talk to a clinician

Seek care soon for signs of high calcium: strong thirst, frequent urination, nausea, constipation, confusion or severe weakness. Get urgent care for confusion, fainting or a very irregular heartbeat.

Questions you could ask

  • Why was this test chosen instead of the 25-hydroxy vitamin D test?
  • Could this be related to my calcium level or to a condition such as sarcoidosis?
  • Should my parathyroid hormone and 25-hydroxy vitamin D be looked at together with this?
  • Could my kidney function be affecting this result?
  • Do we need to check calcium, phosphate and parathyroid hormone?

Questions people ask

Is this the right test to check my vitamin D level?

Usually not. Vitamin D status is checked with the 25-hydroxy vitamin D test. The 1,25 test is for specific situations, such as looking into high calcium or kidney problems. ARUP notes that a normal 1,25 result does not rule out vitamin D deficiency.

Why do reference ranges differ so much between labs?

There is no standard reference material for this test, and immunoassays and mass spectrometry give different results. Compare your result with the range printed on your own report.

How do I convert pg/mL to pmol/L?

Multiply pg/mL by 2.4. For example, 40 pg/mL is about 96 pmol/L. To go the other way, multiply pmol/L by 0.4166.

Show the science and sources

Units

  • 1 pg/mL = 1 pg/mL
  • 1 pg/mL = 2.4 pmol/L

Open the 1,25-Dihydroxy Vitamin D unit converter

For clinicians and researchers

1,25(OH)2D (calcitriol) is the hormonally active metabolite, produced mainly by renal CYP27B1 (1-alpha-hydroxylase) under control of PTH and phosphate/FGF23; macrophages and other cells make it locally, as in sarcoidosis and tuberculosis, where production is not regulated by PTH. Its half-life is reported as about 4-6 hours and its concentration is in the picomolar range, far lower than 25(OH)D, which is in the nanomolar range, so it does not reflect vitamin D stores and is not changed by vitamin D supplementation. No standard reference material or reference measurement procedure exists, so method-specific intervals are recommended: IDS RIA 43-168 pmol/L, IDS iSYS 63-228 pmol/L, LC-MS/MS 59-159 pmol/L (these methods typically measure only the D3 form, and circulating 1,25(OH)2D2 has been reported below about 17 pmol/L); ARUP reports 19.9-79.3 pg/mL (immunoassay) and Quest 18-72 pg/mL for adults (LC-MS/MS). Pediatric levels are higher than adult levels (CALIPER, DiaSorin LIAISON XL: 77-471 pmol/L in the first year, 113-363 pmol/L at 1-3 years and 108-246 pmol/L above 3 years). Clinical uses listed include unexplained hypercalcemia, sarcoidosis and other granulomatous disorders, pseudo-vitamin D deficiency, rickets, tumor-induced osteomalacia, hyperparathyroidism and CYP24A1 deficiency. LC-MS/MS reports may list D2 and D3 forms and a total. ARUP states the test is primarily indicated in evaluation of hypercalcemia and renal failure and that 25-hydroxy vitamin D is the recommended test for diagnosing vitamin D deficiency.

LOINC 1649-3 (primary), 62290-2, 14566-4. Specimen: serum-or-plasma.

Sources

  1. Vitamin D, 1,25-Dihydroxy (test 0080385), ARUP Laboratories
  2. Vitamin D Metabolites: Analytical Challenges and Clinical Relevance, Calcified Tissue International (2022)
  3. Calcitrol 1,25-Dihydroxyvitamin D (Quest Diagnostics send-out test 16558, adult interval as listed by Parkview Health Laboratory), Parkview Health Laboratory

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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