Ethical guidelines for our site UK English US English Polish Italian Hungarian Greek Spanish German Czech Australian English


   
in the news

understanding
your tests

inside the lab

about this site

site map

send us your
comments


home
 


Vitamin D

Formally known as: 25-hydroxy-vitamin D (Calcidiol); 1,25 dihydroxy-vitamin D (Calcitriol)
Related tests: Calcium, Phosphate, Parathyroid Hormone (PTH), Magnesium
The Test Sample
 
What is being tested?
There are two forms of vitamin D that can be measured in the blood - 25 hydroxy-vitamin D and 1,25 dihydroxy-vitamin D.  25 hydroxy-vitamin D is the major form of the hormone found in the blood and is the inactive component from which the active hormone, 1,25 dihyroxy vitamin D is made.  Because 25 hydroxy-vitamin D stays for a long time in the blood and is at a higher concentration than 1,25 dihydroxy-vitamin D, 25 hydroxy-vitamin D is commonly measured to find out about vitamin D status in individuals. The test for 1,25 dihydroxy-vitamin D is used to find out whether the kidney is converting an appropriate amount of inactive 25-hydroxy-vitamin D to the active 1,25 dihydroxy-vitamin D.

Vitamin D comes from 2 sources:  a) produced in the skin on exposure to sunlight (endogenous) and b) that present in foods and supplements (exogenous).  The chemical structures of these types of vitamin D are slightly different and are distinguished by the subscripts in their chemical name.  Vitamin D2 (ergocalciferol) is the form found in foods of animal origin and in most vitamin preparations and supplements while vitamin D3 (cholecalciferol) is the form produced in the body and is also used in some high dose formulations used to treat severe vitamin D deficiency.

Both D2 and D3 vitamin D are converted to the 25-hydroxy vitamin D and then to 1,25 di-hydroxy vitamin D.The main role of vitamin D is to help regulate the absorption of calcium, phosphate, and (to a lesser extent) magnesium. Vitamin D is vital for the growth and health of bone; without it, bones will be soft, malformed, and unable to repair themselves normally, resulting in the disease called rickets in children and osteomalacia in adults. Vitamin D has also been implicated in the regulation of autoimmunity.


How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm. No test preparation is needed.


This page was last modified on May 18, 2009.
 

In the NewsUnderstanding Your TestsInside the Lab
About the SiteSite MapSend Us Your CommentsHome

If you don't know what a word or a medical term means Click Here to link to Mondofacto Online Medical Dictionary

We comply with the HONcode standard for trustworthy health
information:
verify here.

©2004-09 all rights reserved
Email concerns to labtestsonlineuk@acb.org.uk

Terms of Use Privacy