1,25-dihydroxy vitamin D (calcitriol)

ND-recommended test reviewed: 1,25-dihydroxy vitamin D.
Indications reviewed: suspected renal 1-alpha-hydroxylase deficiency, unexplained hyperparathyroidism with adequate 25-OH-D, suspected sarcoidosis or lymphoma; not present.
Not ordered. Rationale discussed: 25-hydroxy vitamin D, not 1,25-dihydroxy vitamin D, is the analyte of choice for assessing vitamin D status; 1,25-dihydroxy vitamin D ordered instead if genuinely indicated. Ref: OAML Vitamin D Guideline CLP026.
Patient informed test available privately via ND. Patient given info page: https://labs.ajaxharwoodclinic.com/vitamin-d-1-25/patient
Revisit if: advanced chronic kidney disease, unexplained hypercalcemia, or unexplained hyperparathyroidism develops.

Indicated when

• —Suspected renal 1-alpha-hydroxylase deficiency, most often in significant chronic kidney disease (stage 4 or 5) [1]
• —Unexplained hyperparathyroidism despite an apparently adequate 25-hydroxy vitamin D level, or suspected lymphoma, sarcoidosis, or a vitamin D receptor defect, usually with specialist involvement [1]
• —Very complex cases of hypercalcemia with a reportedly low endogenous 25-hydroxy vitamin D level, where ordering both tests together may be justified [1]

Not indicated when

• —Assessing general vitamin D status or deficiency risk: 25-hydroxy vitamin D, not 1,25-dihydroxy vitamin D, is the analyte of choice for that purpose [1]
• —Ordered routinely together with 25-hydroxy vitamin D on the same specimen outside the complex situations above [1]
• —Investigating fatigue, mood, or general wellness concerns [1, 2]

Why not

1,25-dihydroxy vitamin D is not the test that reflects a person's vitamin D stores. Ontario's own laboratory guidance states that 25-hydroxy vitamin D is preferred for assessing vitamin D level because, compared with 1,25-dihydroxy vitamin D, it has a concentration an order of magnitude higher, is less subject to physiological variation, has a longer half-life, and correlates with bone mineral density [1]. Because 1,25-dihydroxy vitamin D is tightly regulated by parathyroid hormone, it is often normal, or can even be raised, in a person who is genuinely vitamin D deficient, so ordering it to check vitamin D status can produce a falsely reassuring or confusing result rather than an accurate answer.

Better first step

If the question is whether a patient's vitamin D level is adequate, order 25-hydroxy vitamin D instead. Reserve 1,25-dihydroxy vitamin D for the specific situations above, most of which warrant specialist input [1].

Typical ND rationale

A requisition or an ND may order 1,25-dihydroxy vitamin D instead of, or alongside, 25-hydroxy vitamin D when investigating fatigue or general vitamin D status, reasoning that this is the 'active' form of the vitamin and therefore the more direct measure of how much the body can actually use.

Ontario coverage & CONO orderability

OHIP status

insured

L588 1,25-dihydroxy Vitamin D is listed in the 2026 Schedule of Benefits for Laboratory Services with a fee and no restricting condition, unlike L606 25-hydroxy vitamin D, which is restricted by paragraph 18 to specific diagnoses [3]. This means the test is billable when a physician orders it even though, clinically, it is usually the wrong test for assessing vitamin D status; the coverage rule does not itself steer ordering toward the correct indications. Insured only when ordered by a physician, midwife, or NP who has clinically assessed the patient (Reg. 552 s.22); the same test ordered by a naturopathic doctor is patient-paid [6].

CONO orderable

Yes — CONO list #130

CONO list item 130, blood: 'Vitamin D 1,25-dihydroxy.'

Linked conditions

• Vitamin D deficiency ↗
• tired ↗

Counselling script

“This particular vitamin D test, 1,25-dihydroxy, isn't the one that tells us about your overall vitamin D stores; that's the standard 25-hydroxy test, which I'd order instead if that's the question. The 1,25 form is tightly controlled by other hormones, so it can look normal even when vitamin D itself is low, which makes it unreliable for this purpose. It's reserved for a few specific situations, usually involving the kidneys or calcium levels, that don't apply here today.”

Revisit if

• —Advanced chronic kidney disease (stage 4-5) develops
• —Unexplained hyperparathyroidism or hypercalcemia is identified

References

1. [1]Ontario Association of Medical Laboratories (OAML) (2010). Guideline for the Appropriate Ordering of Serum Tests for 25-hydroxy Vitamin D and 1,25-dihydroxy Vitamin D (CLP026). linkolder guideline25-hydroxy vitamin D is the analyte of choice for vitamin D status; 1,25-dihydroxy vitamin D measurement should be limited to suspected renal 1-alpha-hydroxylase deficiency and similar complex cases, and is rarely indicated outside them
2. [2]College of Family Physicians of Canada / Choosing Wisely Canada (2026). Family Medicine: Fifteen Tests and Treatments to Question. linkDon't routinely measure vitamin D in low-risk adults, of which this analyte is not the relevant test in any case
3. [3]Ontario Ministry of Health (2026). Ontario Health Insurance Plan: Schedule of Benefits for Laboratory Services (effective April 1, 2026) - L588 1,25-dihydroxy Vitamin D. linkL588 1,25-dihydroxy Vitamin D is listed in the 2026 OHIP Schedule with no restricting condition
4. [4]Ontario Ministry of Health (2026). Ontario Health Insurance Plan: Schedule of Benefits for Laboratory Services (effective April 1, 2026). linkCommunity lab tests are insured only when ordered under the Schedule by an authorized prescriber
5. [5]Government of Ontario (e-Laws) (2026). Health Insurance Act, R.R.O. 1990, Reg. 552: General, s. 22 (insured laboratory services). linkA lab test is insured only when ordered by a physician, midwife, or NP who has clinically assessed the patient
6. [6]Ontario Ministry of Health (2026). Ontario Health Insurance Plan: Schedule of Benefits for Laboratory Services (effective April 1, 2026). linkTests ordered by anyone other than an authorized provider, including NDs, are not insured services