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

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

This test measures your body’s level of vitamin D, an important nutrient that helps your bones stay strong and supports overall health.

Quick summary

["Vitamin D helps your body absorb calcium and maintain bone health; low levels may indicate deficiency or poor absorption."]

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

Key facts at a glance

LOINC
110821-6
Short code
FLUBV IgG Msmt Ser
Synonyms
FLUBV IgG 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 doctor may order this test to check if you have enough vitamin D. Common reasons include symptoms like muscle weakness, frequent infections, or if you have a condition that affects vitamin D absorption, such as celiac disease or limited sun exposure.

What Does the Test Involve?

A blood sample is taken from a vein in your arm. The sample is sent to a lab where it is analyzed to measure vitamin D levels. No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if instructed by your doctor.

What Are Common Results?

Results are typically reported as a concentration in nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L). Your doctor will compare your result to a reference range specific to your age and health status.

What Might Low or High Levels Mean?

Low levels of vitamin D may suggest deficiency, which can lead to bone problems, weakened immunity, or other health issues. High levels might indicate over-supplementation or certain medical conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Vitamin D Deficiency and Beyond

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 supplements), certain medical conditions (like malabsorption disorders), or taking medications that interfere with vitamin D metabolism.
Can vitamin D levels be affected by medications?
Yes, some medications—such as anticonvulsants, certain antibiotics, or thyroid replacement therapy—may lower vitamin D levels. Always discuss your medications with your doctor if you’re concerned about vitamin D.
How often should I get this test?
Your doctor will determine how often you need testing based on your health status, risk factors, and symptoms. Typically, people with known deficiencies or certain health conditions may need monitoring more frequently.
  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