25-Hydroxy Vitamin D (Vitamin D)

Clinical Chemistry

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Description

25-hydroxy vitamin D is often measured with calcium, alkaline phosphatase and phosphate to assess skeletal health. Low vitamin D levels are common and are associated with an increased risk of osteomalacia, falls and fracture. There are two main forms of vitamin D - vitamin D3 ( colecalciferol ) and vitamin D2 ( ergocalciferol ). The assay in use at STH measures both 25-OH vitamin D2 and 25-OH vitamin D3. However, measurement of D2 can be variable and total vitamin D may be underestimated in some patients on ergocalciferol. Please see Metabolic Bone guidance on optimising Vitamin D for adult bone health.

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Indications

Indicated in an at-risk individual with clinical suspicion of deficiency because of: Signs/symptoms OR Abnormalities on laboratory investigations suggestive of vitamin D deficiency. Screening for vitamin D deficiency in individuals in at-risk groups who are well is NOT supported by the evidence and is discouraged. Those considered at-risk are: infants and children aged under 5 pregnant and breastfeeding women, particularly teenagers and young women people over 65 people who have low or no exposure to the sun, for example, those who cover their skin for cultural reasons, who are housebound or confined indoors for long periods people with darker skin, for example, people of African, African-Caribbean or South Asian family origin.

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Sample Type

Serum. SST/Gel, minimum 2 mL ( 1 mL separated serum ).

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Reference Range

Action limits in place in STH are as follows:<25 nmol/L: High dose supplementation recommended25 - 50 nmol/L: If bone health an issue, suggest standard dose supplementation. No repeat vitamin D measurement required50 - 125 nmol/L: No action required

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Turnaround Time

Within 2 days

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Testing Frequency

Daily

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References

1. Holick et al. Evaluation, Treatment and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 2011; 96( 7 ):1911 - 1930.2. NICE. PH56 Vitamin D: increasing supplement use among at-risk groups.

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Please note: the above information is subject to change and we endeavour to keep this website up to date wherever necessary.