Skip to content

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, which can affect bone health and other body functions.

Quick summary

["Vitamin D levels help prevent deficiencies that may lead to health risks like bone disorders or weakened immunity."]

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

Key facts at a glance

LOINC
109000-0
Short code
RV IgA Msmt Ser
Synonyms
RV IgA Msmt Ser
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 of vitamin D deficiency, such as muscle weakness, bone pain, or frequent infections. It’s also used to monitor vitamin D levels in people taking supplements or those at higher risk of deficiency, like older adults or those with limited sun exposure.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it involves drawing blood from a vein. If you’re taking vitamin D supplements, check with your provider first to avoid interfering with the results.

What Happens During the Test?

A healthcare professional will insert a small needle into a vein in your arm to draw blood. The process takes a few minutes, and you may feel a brief pinch. The blood sample is then sent to a lab for analysis.

What Are the Results?

Results are typically reported as a numeric value representing the concentration of vitamin D in your blood. Your provider will interpret these results in relation to your symptoms, medical history, and other factors.

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 deficiency?
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 taking certain 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 are ready to discuss the findings.
Can I take vitamin D supplements before the test?
It’s best to avoid taking vitamin D supplements unless instructed by your provider, as they may affect the test results. If you’re unsure, ask your healthcare team for guidance.
  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