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 absorb calcium and maintain bone health. Low levels may indicate deficiency, while higher levels could signal overabsorption or other conditions.
["Vitamin D levels help assess bone health and prevent deficiencies that can cause weakness or fractures."]
Key facts at a glance
- LOINC
- 67807-8
- Short code
- MuV Ag Islt Ql IF
- Synonyms
- MuV Ag Islt 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 of vitamin D deficiency, such as muscle pain, fatigue, or bone pain. It’s also used to monitor vitamin D levels in people at risk, such as those with limited sun exposure, certain medical conditions, or those taking medications that affect vitamin D metabolism.
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 your lab uses a specific method, but this is rare for standard vitamin D testing. Bring any medications you’re taking to your appointment.
During the Test
A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but the process is quick. The blood sample is sent to a lab for analysis.
What the Results Mean
Results are typically reported as a numeric value (e.g., ng/mL or nmol/L) representing your vitamin D concentration. Your provider will compare these numbers to general reference ranges to determine if your levels are within a healthy range or if further action is needed.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Vitamin D deficiency is common and can lead to weakened bones, muscle weakness, or increased risk of certain health issues. High levels may indicate over-supplementation or other metabolic conditions. Your provider will discuss results in the context of your overall health and symptoms.
Short name
Vitamin D Level
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 before the test?
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