Pathology

Test & Collection Guide

Vitamin D Metabolites

Ordering information:

Vitamin D testing can only be requested for a prescribed list of clinical situations (see list below). The request form MUST include the clinical indication for the test. In the absence of this information, testing cannot be performed.

PRESCRIBED LIST OF INDICATIONS FOR VITAMIN D TESTING

Signs or symptoms of osteoporosis or osteomalacia

Increased alkaline phosphatase and otherwise normal LFT's

Hyperparathyroidism, hypo- or hypercalcaemia, or hypophosphataemia;

Malabsorption conditions

Deeply pigmented skin, or chronic and severe lack of sun exposure for cultural, medical, occupational or residential reasons

Taking medication known to decrease 25OH-D levels (for example, anticonvulsants)

Chronic renal failure or renal transplant recipient

<16 years of age with signs or symptoms of rickets

An infant whose mother has established vitamin D deficiency

Exclusively breastfed baby with at least one other risk factor mentioned in this list

Has a sibling who is less than 16 years of age and has vitamin D deficiency

Alternate names:

25 Hydroxy Vitamin D3, 25(OH) Vitamin D, Vit D

Laboratory:

Biochemistry

Test Code:

VITD

Specimen types:

Serum

Container types:

Serum tube with gel

Collection Instructions:

Transport specimen at Room Temperature to lab

Store and transport serum at 4 ^o C

Note: Vitamin D can be added on to the specimens up to 48 hours after the collection (at room temperature) or up to 7 days for specimen stored at 4 ^o C.

Minimum Adult Volume:

1 mL

Notes:

Specimens for vitamin assays must be taken before dietary changes are implemented

Please note: Total Vitamin D measures both Vitamin D2 and D3.

Frequency:

Daily

Result Turnaround Time:

5 hours

Reference Interval:

> 50 nmol/L

Vitamin D levels >50 nmol/L at the end of winter are recommended. Level should be 10-20 nmol/L higher at the end of summer to allow for seasonal decrease.

Vitamin D levels < 50 nmol/L indicate insufficiency. Levels <25 nmol/L indicate significant deficiency.

Sources: RCPA Position Statement May 2019, "Use and Interpretation of Vitamin D testing"

Nowson CA, McGrath JJ, Ebeling PR, et al. Vitamin D and health in adults in Australia and New Zealand: a position statement. Med J Aust 2012; 196: 686-7.

25 Hydroxy Vitamin D3 is the appropriate metabolite to asess in suspected deficiency states.

Occasionally 1,25 di-Hydroxy Vitamin D3 is indicated, but discussion with Chemical Pathologist is required prior to testing by an external provider.

Enquiries - Phone Core Laboratory Box Hill Hospital; 9895 3473

Laboratory Use Only

Storage Instructions:

1,25 di-hydroxyvitamin D, if required, is performed at Austin Pathology and requires a minimum volume of 0.6 mL of serum - Frozen asap