Good vitamin D status is essential for healthy bone metabolism
and modulation of cytokines controlling inflammation.
Deficiency is also associated increased visceral fat,
insulin resistance risk, and weight management difficulties.



Long known for its role in the prevention of childhood rickets1 and in the intestinal absorption of dietary calcium, vitamin D has now been found to be important in protecting the body from a wide range of diseases. Disorders linked with vitamin D deficiency include stroke, cardiovascular disease, osteoporosis, osteomalacia, several forms of cancer, some autoimmune diseases such as multiple sclerosis, rheumatoid arthritis and type I diabetes, and even type 2 diabetes, depression and schizophrenia2-12. A major culprit of vitamin D deficiency is inadequate sun exposure. Vitamin D deficiency is especially problematic for people who spend much of their time indoors, or who live in colder climates.

An easy-to-do home collection bloodspot test for:

Vitamin D2, Vitamin D3, and Total Vitamin D

Accuracy of the Vitamin D Test

  • ZRT uses liquid chromatography/tandem mass spectrometry (LC-MS/MS)31 and participates in DEQAS, the Vitamin D Quality Assessment Scheme, which provides control samples to ensure assay accuracy.
  • Most published studies, on which currently accepted physicians’ recommendations for blood levels are based, have used a radioimmunoassay test from DiaSorin. This test, despite a high correlation with LC-MS/MS for the same samples, usually gives values 20-30% lower than LC-MS/MS.
  • Method accuracy is ensured by standardization with the National Institute of Standards and Technology (NIST) Vitamin D standard reference materials.