Exam used to measure Vitamin D levels?

Question

I need to know more about the exams used to measure Vitamind D levels. What are they called, how exactly do they work, their costs, their accuracy, etc.

I basically need to know everything you can tell me related exams and laboratory tests involving Vitamin D.

Answer 1

To measure Vitamin D levels you can have a simple "Blood test for Vit. D level". There are few blood tests done for that purpose. However, the so called "25-hydroxy vitamin D test" (also called 25-hydroxycalciferol) is the most accurate one in measuring the amount of vitamin D in the body.

25-hydroxy vitamin D is abundant in the blood and changes into an active form (called 1,25-dihydroxy vitamin D). The active form helps control blood levels of calcium and phosphate.

**The circulating Vitamin D is metabolized to 25-hydroxy vitamin D(25-D) by the LIVER and is further metabolized by the KIDNEY to produce the biologically-active form of vitamin D, 1,25-dihydroxy vitamin D (1,25-D). (This is added data after editing....)

The test requires about 5 ml of blood to be extracted from you- you should not eat anything for at least 4 hours prior to blood extraction. The normal value ranges from 16.0 - 74.0 ng/mL.

The test costs about $70 or so. Vitamin Tests are usually not covered by Medicare.

P.S.
>>(Sorry for the error! Million thanks Dr. J for correction. I expanded the details to clear the issue.)

Answer 2

I just wanted to correct one error in Lani's response. 25-hydroxy vitamin D is made in the liver and converted into 1,25 dihydroxyvitamin D in the kidney (and in many other organs and tissues) - not the liver.