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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 use calcium for strong bones and teeth.

Quick summary

["Vitamin D levels help assess your risk for bone-related conditions and overall health."]

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

Key facts at a glance

LOINC
111372-9
Short code
VZV IgM Msmt Ser
Synonyms
VZV IgM 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 This Test Matters

Vitamin D is crucial for maintaining bone health and supporting immune function. Low levels may indicate a deficiency, which can lead to conditions like osteoporosis or muscle weakness. Your doctor may recommend this test if you have symptoms like fatigue, bone pain, or frequent infections.

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 draw if your test involves a fasting sample. Wear a loose shirt for easy access to your arm.

How the Test Works

A healthcare provider will collect a blood sample from your arm. The blood is sent to a lab, where it is analyzed to measure vitamin D levels using a blood test method, often an immunoassay or chemiluminescent immunoassay.

Possible Results and Next Steps

Results are typically reported as a concentration of vitamin D in the blood. If your levels are low, your doctor may recommend dietary changes, supplements, or further testing to determine the cause.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin D level

Frequently asked questions

What causes low vitamin D levels?
Low vitamin D levels can result from insufficient sun exposure, limited dietary intake, certain medical conditions (like malabsorption), or medications that interfere with vitamin D metabolism. High levels may indicate over-supplementation or liver/kidney issues.
How often should I get this test?
Your doctor will determine how often you need this test based on your health status, symptoms, and risk factors. Some people may need it annually, while others may need it less frequently.
Can vitamin D levels change over time?
Yes, vitamin D levels can fluctuate due to changes in sun exposure, diet, or health conditions. Regular monitoring helps track these changes and guide treatment if needed.
  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