What is 25-Hydroxyvitamin D2? High and low values explained.

What is Vitamin D?

Vitamin D is a family of compounds that is essential for the proper growth and formation of teeth and bones.

What are the two different forms of vitamin D:

Two forms of vitamin D can be measured in the blood, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D. The 25-hydroxyvitamin D is the major form found in the blood and is the relatively 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.

Different sources of Vitamin D:

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 the types of vitamin D are slightly different, and they are named vitamin D₂ (ergocalciferol, which comes from plants) and vitamin D₃ (cholecalciferol, which comes from animals). The D₂ form is found in fortified 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 when they are converted by the liver and the kidney into the active form, 1,25-dihydroxyvitamin D.

Some tests do not distinguish D₂ and D₃ forms of the vitamin and report only the total result. Newer methods, however, may report levels of both D₂ and D₃ and then add them together for a total level. This marker here is used to track and interpret vitamin D_2.

Lower levels:

A low blood level of 25-hydroxyvitamin D may mean that a person is not getting enough exposure to sunlight or enough dietary vitamin D to meet his or her body’s demand or that there is a problem with its absorption from the intestines. Occasionally, drugs used to treat seizures, particularly phenytoin (Dilantin), can interfere with the production of 25-hydroxyvitamin D in the liver.