1,25-Dihydroxy Vitamin D (Calcitriol)
Chemical Pathology
Background Information
- 1,25-Dihydroxy Vitamin D (calcitriol, 1,25-Vitamin D) is the most active form of vitamin D, it is formed in the kidney by the action of 1-alpha hydroxylase on 25-hydroxyvitamin D.
- 1,25-Vitamin D may also be produced extra-renally in sarcoidosis, TB, lymphoma and other granulomatous disease.
- 1,25-Vitamin D is not a useful indicator of vitamin D status in most patients, if measurement is indicated, the preferred test for this is 25-hydroxyvitamin D.
- 1,25-Vitamin D may have limited use in the differential diagnosis of hypercalcaemia, possible vitamin D-dependent rickets due to hereditary deficiency of renal 1-alpha hydroxylase or end-organ resistance to 1,25-Vitamin D.
Patient Preparation
No specific preparation required
Sample Requirements
Please contact the duty biochemist before collecting samples to ensure the request is clinically appropriate and the sample is correctly processed.
For adults, blood taken into a 5mL gold top tube (or rust top for the Acute Unit)
Storage/Transport
Do not store. Send at ambient temperature to the laboratory on the day of collection.
Required Information
Relevant clinical details should be provided, including reason for the request.
Turnaround Times
Samples are referred to an external laboratory for analysis with results expected back within 25 working days.
Reference Ranges
Ranges and interpretation reported as provided by referral laboratory.
Further information
To learn more about Vitamin D visit Lab Tests Online
Page last updated: 19/09/2025 | Page last reviewed: 19/09/2025