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

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

This test measures your levels of vitamin D, a nutrient essential for bone health and other bodily functions.

Quick summary

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

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

Key facts at a glance

LOINC
14905-4
Short code
Vit A SerPl-sCnc
Synonyms
Vit A SerPl-sCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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, especially if you have symptoms like muscle weakness, bone pain, or if you’re at higher risk for deficiency (e.g., limited sun exposure, certain medical conditions, or dietary restrictions). It can also be used during pregnancy, before surgery, or to monitor treatment for conditions like osteoporosis.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the blood draw if your lab requires it. Wear comfortable clothing and plan to rest for a few minutes afterward.

What Happens During the Test?

A healthcare professional will insert a small needle into a vein in your arm to draw blood. You may feel a brief pinch, but it usually doesn’t cause significant discomfort. The blood sample is then sent to the lab for testing.

What Are the Results Measured Against?

Results are compared to standard ranges for vitamin D concentration in your blood, though individual ranges may vary slightly by lab. Your provider will interpret the results in relation to your health status and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin D Level

Frequently asked questions

What causes vitamin D levels to be low?
Vitamin D deficiency can result from limited sun exposure, poor diet (low intake of fatty fish, fortified foods, or egg yolks), certain medical conditions (like malabsorption disorders), or medications that interfere with its production or metabolism.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your provider will contact you once they’re ready to review them with you.
Can vitamin D levels be affected by supplements?
Yes, vitamin D supplements (oral or injectable) can raise blood levels, but they may also lead to excess if taken without medical supervision. Always follow your provider’s guidance on dosage and timing.
  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