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3epi25ohd3serplmcnc

Published: August 9, 2026Updated: August 10, 2026

A specialized blood test that measures the 3-epi form of 25-hydroxyvitamin D to accurately assess your true vitamin D status.

Quick summary

{"Measures a specific form (epimer) of vitamin D that can interfere with standard tests","Provides accurate vitamin D measurement especially in children and infants","Helps distinguish between true vitamin D levels and interference from the epimer","May be ordered when standard vitamin D tests show unexpectedly high results","Important for proper diagnosis of vitamin D deficiency or excess"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 10, 2026Editorial policy

Key facts at a glance

LOINC
72403-9
Short code
3-epi-25-OH D3
Synonyms
3-epi-25(OH)D3 SerPl-mCnc
Category
chemistry
Sample
serum
Container
Serum separator tube (SST) or plain red top tube
Units
N/A
Ref low
0.2
Ref high
6.5
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Liquid chromatography-tandem mass spectrometry (LC-MS/MS)
CPT
82306
SNOMED
41355002
Specimen volume
1.0 mL minimum, 2.0 mL preferred
Stability
Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days. Avoid repeated freeze-thaw cycles.
Hemolysis max
50
Lipemia max
100
Icterus max
20
TAT
48–168 hours
Order
routine

What is this test?

The 3-epi-25-hydroxyvitamin D3 test measures a specific form of vitamin D called 3-epi-25-hydroxyvitamin D3 in your blood. This is a stereoisomer (a mirror image version) of the standard 25-hydroxyvitamin D, which is the main form of vitamin D measured to check your vitamin D status. While the 3-epi form is present in everyone in small amounts, some people—particularly infants, young children, and certain adults—may have higher levels that can affect standard vitamin D test results.

How is this test performed?

A healthcare professional will draw a small blood sample from a vein in your arm. The blood is collected into a tube and sent to a laboratory for analysis. You do not need to fast before this test. The laboratory will specifically measure the 3-epi-25-hydroxyvitamin D3 separate from the regular 25-hydroxyvitamin D to give your doctor a complete picture of your vitamin D status.

Why might I need this test?

Your doctor may order this test if your standard vitamin D test shows unexpectedly high levels, or if there is suspicion that the 3-epi form may be interfering with your results. This is more common in infants and young children. The test is also useful when accurate vitamin D assessment is critical for treatment decisions, such as when diagnosing vitamin D deficiency or monitoring vitamin D supplementation therapy.

Reference range

Reference range varies by method and laboratory; typically 0.2-6.5 ng/mL (0.5-16.3 nmol/L) for 3-epi-25-hydroxyvitamin D3. Results should be interpreted in context with total 25-hydroxyvitamin D and clinical presentation.N/A

Specimen: serum

No special preparation required. Fasting is not necessary. Maintain standard hydration. Inform healthcare provider of any vitamin D supplements or medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

What is the difference between this test and a regular vitamin D test?
A regular 25-hydroxyvitamin D test measures the total amount of vitamin D but may not distinguish between the standard form and the 3-epi form. This specialized test specifically measures only the 3-epi-25-hydroxyvitamin D3, allowing your doctor to determine how much of your total vitamin D reading comes from this epimer and calculate your true vitamin D status.
Who should have this test?
This test is particularly important for infants, young children, and neonates, who naturally have higher levels of the 3-epi form. It may also be ordered for adults when standard vitamin D tests show unusually high results that don't match clinical symptoms, or when accurate vitamin D measurement is essential for managing conditions like osteoporosis, kidney disease, or parathyroid disorders.
Does having a high 3-epi-25-hydroxyvitamin D3 level mean I have too much vitamin D?
Not necessarily. The 3-epi form has different biological activity than the standard 25-hydroxyvitamin D. While it can interfere with standard test results, its clinical significance is still being studied. Your doctor will interpret your results in context, considering both the epimer level and the standard vitamin D measurement, to determine your true vitamin D status.
Do I need to prepare for this test?
No special preparation is typically needed. You can eat and drink normally before the test. However, it's important to inform your doctor about any vitamin D supplements or medications you are taking, as these may affect the results.
  1. 1
    Mayo Clinic Laboratories - 3-Epi-25-Hydroxyvitamin D3Source
  2. 2
    LOINC Code 72403-9 ReferenceSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 10, 2026. · Read our editorial policy