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Serum or plasma concentration of vitamin D (25-hydroxyvitamin D)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of vitamin D in your blood. Vitamin D is important for bone health and immune function.

Quick summary

["Vitamin D helps keep bones strong and supports immune health—low levels may indicate deficiency."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
29849-7
Short code
JCV IgM Ser-aCnc
Synonyms
JCV IgM Ser-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to check if you have enough vitamin D. This can happen if you don’t get enough sunlight, have limited exposure to sunlight, or have certain medical conditions that affect vitamin D absorption.

What to Expect Before the Test

No special preparation is needed. You may have a blood sample drawn from a vein in your arm. If you’re taking vitamin D supplements, let your provider know, as this may affect results.

What the Results Mean

Results help determine if your vitamin D levels are within a healthy range. Low levels may suggest deficiency, which can lead to health issues like bone problems or weakened immunity.

Common Causes of Low or High Levels

Low vitamin D levels can result from limited sun exposure, certain medications, or conditions that affect digestion. High levels may occur from overuse of supplements or certain medical treatments.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin D level

Frequently asked questions

How often should I get this test?
Your provider will decide based on your health needs. Typically, it’s done once a year for adults with risk factors (like limited sun exposure or certain medical conditions).
What if my results are low?
If your levels are low, your provider may recommend dietary changes, increased sun exposure, or supplements to improve them. Follow-up tests may be needed to monitor progress.
Does diet affect this test?
Yes, foods rich in vitamin D (like fatty fish, fortified dairy, or egg yolks) can influence results. Avoiding supplements unless prescribed by your provider can help ensure accurate testing.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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 16, 2026. · Read our editorial policy