Vitamin D, 25-Hydroxy

Clinical Background

Vitamin D is a group of fat soluble prohormones that play a vital role in maintenance of bone health. It also plays a role in proper functioning of the immune system, cancer prevention and cardiovascular disease prevention. Several forms of vitamin D exist, with the major forms being vitamin D2 and vitamin D3. Vitamin D2 is not produced by the body, but is found only in the diet from fish or plants or by supplementation. Vitamin D3 is formed in the skin upon exposure to sunlight and is also found in the diet consisting of animal products.

Vitamin D levels are determined based on the serum concentration of the major circulating form of vitamin D, 25-hydroxy-vitamin D. Deficiencies in vitamin D can lead to an increased risk of bone loss or bone fractures. Recent studies have shown that vitamin D deficiency may play a role in many other diseases as well.


Metabolon is now offering a Vitamin D, 25-Hydroxy test in its CLIA laboratory. The test method is tandem mass spectrometry (LC/MS/MS), which differentiates between vitamin D2 and D3 forms. Concentrations of each form of vitamin D are reported, in addition to the total vitamin D concentration.

Sample collection Information

Please contact Metabolon at for sample collection instructions.


This test should not be used on children less than one year of age due to the presence of interfering 3-epi-25-hydroxy vitamin D forms in this population. There is no interference due to hemoloysis, icterus or lipemia.

Total Vitamin D (25-hydroxy) Interpretation Ranges

<20 ng/ml Deficiency
20-29 ng/ml Moderate to mild deficiency
30-80 ng/ml Optimal level
>80ng/ml Elevated level (possible toxicity)


Hathcock J, Shao A, Vieth R, Heaney R. Risk Assessment for Vitamin D. Am J Clin Nutr 2007; 85:6-18.
Holick, M. Vitamin D Deficiency. N Eng J Med 2007; 357:266-281.

For questions about this test contact us at