Calcitriol (1,25-dihydroxyvitamin D)
Also called: Calcitriol, 1,25-dihydroxyvitamin D, 1,25(OH)2D, Active vitamin D
The active, hormone form of vitamin D, made mainly by the kidneys. This is a specialist test, quite different from the usual vitamin-D blood test — it is measured to work out unusual calcium problems, certain kidney and parathyroid disorders, and some rare conditions, not to check ordinary vitamin-D status.
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What does Calcitriol (1,25-dihydroxyvitamin D) measure?
Vitamin D from sun and diet is first turned into a storage form (25-hydroxyvitamin D — the one measured by the ordinary 'vitamin D' test), and then activated by the kidneys into calcitriol (1,25-dihydroxyvitamin D), the true hormone that raises blood calcium by boosting its absorption from the gut. Because activation is tightly controlled by the parathyroid hormone, phosphate and the kidneys, the calcitriol level does not track vitamin-D intake and is a poor test of everyday vitamin-D status — the ordinary 25-hydroxyvitamin D test is used for that. Calcitriol is instead a specialist test reserved for specific puzzles: unexplained high or low blood calcium, working out why calcium is abnormal in kidney disease, certain inherited disorders of vitamin-D handling, and conditions such as sarcoidosis or some lymphomas where cells make extra calcitriol and drive calcium up. It is always interpreted together with calcium, phosphate, PTH and the ordinary vitamin-D level, by a specialist.
What does a high Calcitriol (1,25-dihydroxyvitamin D) level mean?
- Sarcoidosis and some other granulomatous diseases — the tissue makes extra active vitamin D, raising calcium.
- Some lymphomas — similar mechanism.
- Primary hyperparathyroidism — high PTH drives activation.
- Certain rare inherited disorders — of vitamin-D handling.
What does a low Calcitriol (1,25-dihydroxyvitamin D) level mean?
- Chronic kidney disease — the failing kidney can't activate vitamin D; a key cause of low calcium in kidney disease.
- Hypoparathyroidism — low PTH means less activation.
- Certain inherited disorders — where the activating step is deficient (a form of rickets).
When to discuss with a doctor
Calcitriol is not the test to check whether your vitamin D is 'low' — that is the ordinary 25-hydroxyvitamin D test. Calcitriol is a specialist investigation ordered by an endocrinologist, kidney doctor or other specialist to solve specific problems: an unexplained abnormal blood calcium, understanding calcium and bone disturbances in kidney disease, or looking for conditions like sarcoidosis that overproduce it. It is always read alongside calcium, phosphate, PTH and the ordinary vitamin-D level rather than alone. Mediora.AI shows calcitriol in the context of those related markers so the calcium-regulation pattern is visible; if it was measured, the interpretation belongs with the specialist who ordered it.
Related markers
Commonly confused with
- Vitamin D (25-OH) Calcitriol is not another vitamin D test. The usual test measures the storage form, which shows your reserves; calcitriol is the active hormone the kidneys make from it, and it is ordered for kidney and calcium problems, not to check your levels.