Vitamin D2 & D3, again

I have read the earlier topic on D2 & D3, the pdf cited in that topic, and the technical brief in the LOINC users guide, but I still have a question. For basic Vitamin D testing, I think I’m supposed to be using 25-hydoxycalciferol for what’s reported as “D2” and calcidiol for “D3”. What about the total of 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3?


Putting the term 25 hydroxyvitamin D2 D3 into RELMA brings up the Calcidiol+Calciferol terms. The plus sign indicates that both analytes are included in the one measurement being the “total” value. There are MCNC and SCNC properties available for you to choose from.

Hope this helps, and have a great week!

So if, and I’ll admit that’s a big if, I’m right that the D2 tested would be 25-hydroxycalciferol and the D3 testsed is calcidiol, then why isn’t the total 25-hydroxycalciferol+calcidiol? Seems wrong to say calciferol instead of 25-hydroxycalciferol.

The Vitamin D nomenclature in literature is very difficult. Before you go down any “IF” path, may I suggest you confirm with your biochemist/medical director what is truly analyzed in your laboratory. If multiple result fields are reported for the different active and storage forms of Vitamin D, outline them appropriately.

Taking an approach of defining exactly what’s measured and what you’re looking for BEFORE starting to map to LOINC keeps your time and effort efficiency aligned with everything else on your work calendar.