FAQs Vitamin D

FAQs Vitamin D

What is being tested?

How is the sample collected for testing?

What are the sources and forms of Vitamin D ?

How is the sample collected?

What is being tested?

There are two forms of vitamin D that can be measured in the blood, 25-hydroxyvitamin D [25(OH)D] (D2)and 1,25-dihydroxyvitamin D [1,25(OH)(2)D](D3). 25-hydroxyvitamin D is the major form of the hormone found in the blood and is the inactive precursor to the active hormone, 1,25-dihydroxyvitamin D. Because of its long half-life and higher concentration, 25-hydroxyvitamin D is commonly measured to assess and monitor vitamin D status in individuals.Vitamin D comes from two sources: endogenous, which is produced in the skin on exposure to sunlight, and exogenous, which is ingested in foods and supplements. The chemical structures of these types of vitamin D are slightly different, and they are named vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The D2 form is found in foods and in most vitamin preparations and supplements. Vitamin D3 is the form produced in the body and is also used in some supplements. Vitamin D2 and D3 are equally effective.

Many tests for 25-hydroxyvitamin D do not distinguish D2 and D3 forms of the vitamin and report only a total 25-hydroxyvitamin D. Newer methods, however, may report levels of both 25-hydroxy D2 and D3 and then add them together for a total 25-hydroxyvitamin D level. Total 25-hydroxyitamin D concentration is what is used to assess vitamin D status.

What are the sources and forms of Vitamin D ?

The main role of Vitamin D is to help regulate the absorption of calcium, phosphorus, 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 diseases called rickets in children and osteomalacia in adults. Vitamin D has also been implicated in the regulation of autoimmunity, metabolic function, and cancer prevention.

How is the sample collected for testing?

A blood sample is obtained