25-hydroxyvitamin D


Alternative names, keywords

Vitamin D, 25-hydroxy vitamin D, 25-OH vitamin D, 25 OHD

Samples required

5 mL clotted blood. Smaller tubes are available for paediatric samples.

Avoid haemolysis.

Test indications

For investigation of suspected vitamin D deficiency or toxicity.

When giving vitamin D and rechecking the serum concentration, please state what preparation is being taken.

Test information

Assay detects both D3 (cholecalciferol) and D2 (ergocalciferol) forms.

Factors affecting test performance/ results

Haemolysis may cause interference - potentially affected results (serum Hb > 2g/L) will be blocked..

Biotin may interfere - samples should not be taken from patients receiving therapy with high biotin doses (i.e. > 5 mg/day) until at least 8 hours following the last biotin administration.

In rare cases, interference due to extremely high titres of antibodies to analyte-specific antibodies, streptavidin or ruthenium can occur.

Results should always be assessed in conjunction with the patient’s medical history, clinical examination and other findings.

Reference range

50 - 120 nmol/L

Expert opinion advocates a vitamin D level of >75 nmol/L in individuals with osteoporosis.

Turnaround time

RSCH same day, PRH one working day


Biochemistry (Automation)