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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 is important for bone health and other bodily functions.

Quick summary

["Vitamin D helps maintain strong bones and supports immune function."]

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

Key facts at a glance

LOINC
86592-3
Short code
VZV Ag Tiss Ql IF
Synonyms
VZV Ag Tiss Ql IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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 muscle weakness, bone pain, or if you’re at risk for vitamin D deficiency. It’s also used to monitor vitamin D levels in people taking supplements or those with conditions affecting vitamin D absorption.

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 your blood is drawn early in the morning. Wear comfortable clothing and plan to stay for about 15 minutes while the blood is drawn.

During the Test

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

What the Results Mean

Results are typically reported in nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L). Your provider will discuss the numbers with you and compare them to your individual health needs.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low vitamin D levels can lead to weakened bones, muscle pain, fatigue, or increased risk of certain diseases. High levels may indicate over-supplementation or other health concerns. 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, certain medical conditions (like malabsorption disorders), or taking medications that interfere with vitamin D metabolism.
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 your results.
Can I take vitamin D supplements to raise my levels?
Yes, but only under medical supervision. Too much vitamin D can be harmful, so your provider will guide you on safe dosage and monitoring.
  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