Pathology Handbook

25-hydroxycholecalciferol (vitamin D)

Synonyms

25-OHCC, 25OH-D

Clinical Indications

25-hydroxycholecalciferol (25-D), the hepatic precursor to the biologically active 1,25 dihydroxycholecalciferol (1,25-D), is the major circulating metabolite of vitamin D.

Measurement of 25-D provides a satisfactory index of vitamin D status for investigation of patients with suspected osteomalacia, rickets or suspected vitamin D toxicity

Test Includes

Vitamin D requests will also generate a bone profile and PTH

Request Form 

Request on ICE

Availability

Analyzed if specific criteria met.

Specific Criteria

Investigation of suspected vitamin D deficiency or toxicity.

Sample will be rejected if repeated within 3 months of starting Vitamin D therapy.

Patient Preparation

A fasting sample is preferred but not essential. No further dietary or drug restrictions are required.

Turnaround Time

7 days

Specimen

Serum in GOLD top vacutainer (adults) or GREEN top vacutainer (paediatrics)

Volume

5 ml

Container

Adults

 Vacutainer gold top

Paediatrics

Vacutainer green top

Collection

Samples should be transported to laboratory as quickly as possible.

Vitamin D is stable in whole blood for up to 3 days, so a separation delay does not invalidate the result.

Samples sent to Basildon Hospital or the Royal London Hospital.

Causes for Rejection

Not meeting specific criteria for analysis. Delay in sample reaching laboratory.  

Interpretation

Less than 25 nmol/L: 

Profound Vitamin D deficiency (associated with a high risk of osteomalacia or rickets)

Between 25-75 nmol/L: 

Vitamin D insufficiency

Between 76-150 nmol/L:

Vitamin D sufficient

Greater than 150 nmol/L:

Vitamin D sufficient but consistent levels above 250 nmol/L are associated with toxicity

 

For Vitamin D in renal patients the consultants require Vitamin D2 and Vitamin D3 levels as well as total Vitamin D. When requesting in ICE this will be on the Renal/Urology page