Frequently Asked Questions about Quest Diagnostics Vitamin D Test Services

Did you know that Quest Diagnostics provides testing services for Vitamin D? Keep reading for helpful information about Vitamin D and how Quest Diagnostics tests patients for this vitamin.

About Vitamin D Testing

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that is made by the body after exposure to ultraviolet rays from the sun. Vitamin D can also be obtained by taking supplements and from eating certain foods.

What does Vitamin D do in the body?

Vitamin D helps maintain normal blood levels of calcium and phosphorous. It aids in the absorption of calcium, helping to form and maintain strong bones. Vitamin D also modulates neuromuscular, immune and other cellular functions.

What does Vitamin D testing assess?

Vitamin D tests generally assess the total volume of 25-Hydroxyvitamin D (25OHD), which is the form of Vitamin D circulating in blood. Vitamin D tests may also provide information on the levels of Vitamin D2 and D3, which comprise total Vitamin D levels.

Why do physicians test for Vitamin D?

A physician generally will order a test to determine the level of Vitamin D in a patient's body. A physician would typically evaluate a test result in connection with several other factors affecting a patient's health, such as medical history, gender and age.

Quest Diagnostics Vitamin D Test

How does Quest Diagnostics test for Vitamin D?

Quest Diagnostics offers two test methods. The first method is an immunoassay, which measures total vitamin D. This test is appropriate for all patients not been prescribed D2. The second method is called liquid chromatography tandem mass spectrometry, also known as LC/MS/MS. This is appropriate for people who have been prescribed D2.

Are both immunoassay and LC/MS/MS reliable test methods for Vitamin D?

Yes, scientific literature indicates that both tests are highly accurate and reliable methods for measuring vitamin D.

What information does the Quest Diagnostics Vitamin D test provide?

Our Vitamin D test results provide the total level of Vitamin D found in a patient's blood serum, and the diagnostic category, such as Vitamin D deficient or sufficient, indicated by the total level. We also provide information on the levels of Vitamin D2 and Vitamin D3 in blood serum.

What does ng/ml represent?

A nanogram is one billionth of a gram. ng/ml refers to the number of nanograms per milliliter of fluid.

What are Vitamin D2 and Vitamin D3?

Vitamin D2 is derived from fungal and plant sources, and is commonly found in supplements, such as multivitamins, in the U.S. Vitamin D2 may also be used in the pharmacological treatment of Vitamin D deficiency. Vitamin D3 is derived from animal sources and is made in the skin following exposure to sunlight. The LC/MS/MS technique is able to directly quantify Vitamin D2 and Vitamin D3. By comparison, immunoassay-based Vitamin D tests can only indirectly measure Vitamin D2 and Vitamin D3.

What information does Quest Diagnostics provide to physicians about the company's Vitamin D test?

Physician clients receive a Test Summary that describes our Vitamin D test and how it can be used.

How to get a Vitamin D Test through Quest Diagnostics

How can I be tested for Vitamin D through Quest Diagnostics?

In most states, a physician must provide a patient a requisition for testing to be performed. A patient may present a requisition and provide a blood sample at any one of our approximately 2,100 patient service centers.

Can I schedule an appointment to provide a sample?

Yes. Quest Diagnostics is the only national diagnostic testing company that provides nationwide appointment scheduling.

What does testing involve?

Once your physician gives you a prescription for testing, visit one of our convenient Patient Service Centers to provide a blood sample for testing.

Do I have to fast before I submit a sample for Vitamin D testing?


Dated October 2008

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