25-hydroxycholecalciferol (vitamin D)
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
Vitamin D requests will also generate a bone profile and PTH
Request on ICE
Analyzed if specific criteria met.
Investigation of suspected vitamin D deficiency or toxicity.
Sample will be rejected if repeated within 3 months of starting
Vitamin D therapy.
A fasting sample is preferred but not essential. No further
dietary or drug restrictions are required.
Serum in GOLD top vacutainer (adults) or GREEN top vacutainer
Samples should be transported to laboratory as quickly as
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
Causes for Rejection
Not meeting specific criteria for analysis. Delay in sample
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