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Test ID 2425D 25-Hydroxyvitamin D:24,25-Dihydroxyvitamin D Ratio, Serum

Ordering Guidance

Please consider the 25HDN or DHVD tests for Vitamin D assessment. The 25-hydroxyvitamin D test (25HDN / 25-Hydroxyvitamin D2 and D3, Serum) in serum is the preferred initial test for assessing vitamin D status and most accurately reflects the body's vitamin D stores. In the presence of renal disease or hypercalcemia, testing of 1,25-dihydroxy vitamin D (DHVD) might be needed to adequately assess vitamin D status.

Specimen Required


Preferred: Red top

Specimen Volume: 3 mL

Collection Instructions: Spin down within 2 hours of draw.

Useful For

As a screening test for inactivating CYP24A1 mutations in patients with symptoms, signs, or biochemical findings of parathyroid hormone (PTH)-independent hypercalcemia or hypercalciuria

Profile Information

Test ID Reporting Name Available Separately Always Performed
2425R 24,25 Dihydroxy Vitamin D No Yes
25HDN 25-Hydroxyvitamin D2 and D3, S Yes Yes

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Portions of this test are covered by patent(s) held by Quest Diagnostics

Reporting Name

25HDN:24,25 Dihydroxy VitD Ratio, S

Specimen Type


Specimen Minimum Volume

1.1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
  Frozen  30 days
  Ambient  7 days

Reference Values

Interpretative commentary provided based on 25-hydroxyvitamin D (25HDN) to 24,25-dihydroxyvitamin D (24,25D) ratio result.


25HDN to 24,25D ratio less than 25*

*Interpretation: Normal (Ratio of less than 25 may also be observed in heterozygous carriers of CYP24A1 mutations)


25HDN to 24,25D ratio between 25-80**

**Interpretation: Ratios in the 25 to 80 range can be seen in patients with low vitamin D or heterozygous CYP24A1 mutations. Confirmation with molecular testing is recommended.


25HDN to 24,25D ratio greater than 80***

***Interpretation: Ratios greater than 80 indicate probable biallelic CYP24A1 mutation or deletion. Confirmation with molecular testing is recommended.


Reference values not applicable for 24,25 Dihydroxyvitamin D Total result.


Results should be interpreted in the context of other biochemical findings including serum calcium, parathyroid hormone, and 1,25 dihydroxyvitamin D concentrations. If 25-OH-D is less than 20 ng/ml the ratio of 25-OH-D to 24,25-dihydroxyvitamin D will be falsely elevated since there is no inactivation 25-OH-D to 24,25-dihydroxyvitamin D.

Day(s) Performed


Report Available

2 to 6 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information



LOINC Code Information

Test ID Test Order Name Order LOINC Value
2425D 25HDN:24,25 Dihydroxy VitD Ratio, S 94674-9


Result ID Test Result Name Result LOINC Value
2897 25-Hydroxy D2 49054-0
63416 25HDN:24,25 Dihydroxy VitD Ratio, S 94673-1
2898 25-Hydroxy D3 1989-3
83670 25-Hydroxy D Total 62292-8
90601 24,25-Dihydroxy VitD Total 94672-3

NY State Approved