Serum or plasma concentration of vitamin D (25-hydroxyvitamin D)
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, affecting bone health or other health conditions.
["Vitamin D levels help assess bone health and potential deficiencies that could impact overall well-being."]
Key facts at a glance
- LOINC
- 31982-2
- Short code
- VZV Ag Spec Ql
- Synonyms
- VZV Ag Spec Ql
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- 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 bone pain, muscle weakness, or if you’re at higher risk for vitamin D deficiency (e.g., limited sun exposure, certain medical conditions, or dietary habits). It’s also used to monitor vitamin D levels after treatment or supplementation.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if your lab uses a different protocol. Wear comfortable clothing and avoid heavy meals or caffeine before testing.
What Happens During the Test?
A healthcare professional will draw blood from a vein in your arm. The process takes a few minutes, and you may feel a brief pinch. The blood sample is sent to a lab for analysis.
What Are the Results?
Results are typically reported as a concentration of vitamin D in the blood, measured in nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L). Your provider will interpret the results in relation to your health status and symptoms.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Vitamin D deficiency can lead to weakened bones (osteomalacia or rickets), increased risk of fractures, or other health issues like fatigue or immune problems. High levels may also cause symptoms like nausea or kidney stones. Your provider will discuss results with you based on your medical history and needs.
Short name
Vitamin D level (25-OH vitamin D)
Frequently asked questions
What causes vitamin D levels to be low?
How long does it take to get results?
Can I take vitamin D supplements if my levels are low?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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