Chemical Pathology


1,25 dihydroxyvitamin D (calcitriol; 1,25 D3) is the most active form of vitamin D formed in the kidney by the action of 1-α hydroxylase on 25-hydroxyvitamin D, but may also be produced extra-renally in sarcoidosis, TB, lymphoma and other granulomatous disease.

1,25 D3 is not a good indicator of vitamin D status in most patients. The preferred test for this is 25-hydroxyvitamin D.

1,25 D3 may have limited use in the differential diagnosis of hypercalcaemia, or in investigation of possible vitamin D-dependent rickets due to hereditary deficiency of renal 1-alpha hydroxylase or end-organ resistance to 1,25-dihydroxyvitamin D.

Sample requirements


Please contact the duty biochemist before collecting samples to ensure the request is appropriate.

It is also necessary to make contact so that the laboratory is alerted and to avoid confusion with 25-OHD.

For adults, blood taken into a 5mL gold top tube (or rust top for the Acute Unit)

Gold top with cap


Do not store. Send at ambient temperature to the laboratory on the day of collection.

Required information

Please discuss all requests with the duty biochemist before sending samples.

Relevant clinical details should be provided, including reason for the request.

Turnaround times

Samples are sent to a referral laboratory for analysis with results expected back within 2 weeks.

Reference ranges

Desirable level: >60 nmol/L

Further information

To learn more about access the vitamin D monograph of the Association for Clinical Biochemistry and Laboratory Medicine

Page last updated: 19/11/2020