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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, which helps your body use calcium and maintain strong bones. Low levels may indicate deficiency, affecting bone health and other body functions.

Quick summary

["Vitamin D levels help prevent deficiencies that can lead to bone problems or other health risks."]

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

Key facts at a glance

LOINC
7966-5
Short code
MuV IgG Ser-aCnc
Synonyms
MuV IgG 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 doctor may order this test if you have symptoms like muscle weakness, bone pain, or if you’re at higher risk for vitamin D deficiency—such as not getting enough sunlight, having limited sun exposure, or having certain medical conditions.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it involves drawing blood. Wear a comfortable shirt for easy access to your arm.

What Happens During the Test?

A healthcare provider will insert a small needle into your arm to draw blood. You may feel a brief pinch, but it’s over quickly. The blood is then sent to a lab for testing.

What Are the Possible Results?

Results are compared to standard ranges for your age and health status. Low levels may need supplements or dietary changes, while high levels could indicate overuse of supplements or certain medical conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

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’s processing time. Your doctor will contact you once they’re ready.
Can I take vitamin D supplements before my test?
If your doctor prescribed supplements, follow their instructions. If you’re unsure, ask your provider whether to stop or adjust your dose before testing to avoid misleading results.
What symptoms might indicate vitamin D deficiency?
Common signs include fatigue, muscle weakness, bone pain, frequent infections, or mood changes. If you experience these symptoms, discuss them with your doctor, who may recommend 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