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Vitamin D Index (Serum)

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

This test measures your body’s level of vitamin D, a nutrient important for bone health, muscle function, and immune support.

Quick summary

["Vitamin D helps maintain strong bones and supports overall health; low levels may indicate deficiency."]

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

Key facts at a glance

LOINC
104456-9
Short code
VZV IgA index Ser+CSF-aCnc
Synonyms
VZV IgA index Ser+CSF-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 if you have symptoms like fatigue, muscle weakness, or bone pain, or if you’re at higher risk for vitamin D deficiency (e.g., limited sun exposure, certain medical conditions, or dietary habits). It’s also used to monitor vitamin D levels after treatment for deficiency.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, usually drawn from your arm. If you’re on blood thinners, let your provider know before the test.

What the Results Mean

Results help determine if your vitamin D levels are sufficient, insufficient, or very low. Your provider will interpret the results in relation to your health and symptoms.

Common Causes of Low Vitamin D

Vitamin D deficiency can result from limited sun exposure, poor diet, certain medical conditions (e.g., malabsorption disorders), or medications that interfere with its production.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin D plays a critical role in bone health by helping your body absorb calcium. Low levels may increase fracture risk, weaken muscles, or contribute to conditions like osteoporosis or rickets in children. It also supports immune function and may influence mood and energy levels. Your provider may recommend supplements or lifestyle changes if levels are low.

Short name

Vitamin D Level

Frequently asked questions

How long does it take to get my vitamin D test results?
Results are typically available within 1–3 business days, depending on your lab and provider. Follow-up may be scheduled if further testing or adjustments are needed.
Can I eat or drink anything before this test?
You can eat and drink normally before the test, as no fasting is required. However, if your provider gave specific instructions, follow them.
What should I do if my vitamin D levels are low?
If your levels are low, your provider may recommend dietary changes (e.g., fortified foods, fatty fish), sunlight exposure, or supplements under medical supervision to avoid overuse.
  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