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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 absorb calcium and maintain strong bones.

Quick summary

["Vitamin D levels help prevent bone-related health issues and support overall wellness."]

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

Key facts at a glance

LOINC
110881-0
Short code
VZV DNA Msmt Amn
Synonyms
VZV DNA Msmt Amn
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider 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 or having limited sun exposure. It’s also used to monitor vitamin D levels in people taking supplements or those with 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 test if it’s done on an empty stomach. Bring any medications you’re currently taking to your appointment.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause discomfort. The blood sample is then sent to a lab for testing.

What Are the Results?

Results are typically reported in nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L). Your provider will interpret these results in relation to your health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low vitamin D levels can lead to weakened bones, increased risk of fractures, or other health issues like fatigue or muscle pain. High levels may indicate over-supplementation or certain medical conditions. Regular monitoring helps manage these risks effectively.

Short name

Vitamin D level

Frequently asked questions

What causes vitamin D deficiency?
Vitamin D deficiency can result from limited sun exposure, poor diet (low intake of fatty fish, fortified foods, or supplements), certain medical conditions (like malabsorption disorders), or being confined to bed for long periods.
How long does it take to get results?
Results are usually available within 1–3 business days, depending on your lab’s processing time. Your provider will contact you once they’re ready to discuss the results.
Can I take vitamin D supplements before the test?
Yes, but inform your healthcare provider beforehand. They may advise adjusting your supplement timing or dosage to ensure accurate results.
  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