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Lab test

Cardio IQ® Vitamin D, 25-Hydroxy Test

The Cardio IQ® Vitamin D, 25-Hydroxy test measures 25-hydroxy vitamin D in a blood serum sample, reporting the naturally occurring D3 form and the D2 analog form separately. Quest describes it as a good index of circulating vitamin D activity in people without kidney disease.

Blood drawFasting preferredQuest patient service center

About this test

This test measures 25-hydroxy vitamin D using liquid chromatography tandem mass spectrometry (LC/MS/MS), a method that separately measures the D3 and D2 forms of the vitamin. D3 is the form the body makes naturally or gets from diet, while D2 is the analog form sometimes used to address vitamin D3 deficiency.

Quest describes serum 25-OH vitamin D as a good index of circulating vitamin D activity in people who do not have kidney disease. Levels lower than typical can come from dietary deficiency, poor absorption or impaired liver metabolism of the vitamin, and Quest associates this with bone conditions such as rickets and osteomalacia, while levels higher than typical can lead to hypercalcemia.

Test details

Quest code91735
MethodologyChromatography/Mass Spectrometry
Sample type0.5 mL serum
Patient preparationFast before your blood draw if you can; water is fine.
CollectionQuest patient service center

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Quest resources

Additional details

What this test looks at

The test reports three values: 25-OH vitamin D2, 25-OH vitamin D3 and the total of the two, measured in a 0.5 mL serum sample by LC/MS/MS. Quest also lists this test as Vitamin D, 25-Hydroxy, LC/MS/MS, Cardio IQ®.

Order online and a physician order is included — no doctor's visit and no insurance needed. Your sample is collected at a Quest Diagnostics patient service center.

Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.

Frequently asked questions

What does this test measure?

It measures 25-hydroxy vitamin D in serum, reporting the D2 and D3 forms separately along with a total, using liquid chromatography tandem mass spectrometry.

How is the sample collected?

The test uses a 0.5 mL serum sample from a routine blood draw.

Do I need to prepare for this test?

Fast before your blood draw if you can; water is fine. This is the preparation Quest publishes for this test; if your clinician gives you different instructions, follow theirs.

Why does this test report vitamin D2 and D3 separately?

D3 is the form the body makes or gets from diet, while D2 is the analog form sometimes used to address vitamin D3 deficiency. Reporting them separately, along with a total, gives a clinician more detail than a single combined vitamin D number.

How much does the Vitamin D, 25-Hydroxy Cardio IQ test cost?

The cash price at Celio Health is $225. That covers the physician's order and sample collection at a Quest patient service center — no insurance is needed and there's no separate doctor's visit to pay for.

Last updated 2026-09-18 · How we write about lab testing

Educational content

This page is for general educational purposes only. It is not medical advice, and it is not a substitute for consultation with a qualified healthcare professional. Laboratory results should always be interpreted by a licensed clinician who knows your health history. If you have questions about your health or your results, talk with your doctor. If you think you may be experiencing a medical emergency, call 911.