25-Hydroxyvitamin D (25(OH)D) blood test
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 vitamin D deficiency.
["Vitamin D levels help assess bone health and potential deficiency."]
Key facts at a glance
- LOINC
- 49591-1
- Short code
- VITDINT
- Synonyms
- Calcidiol & Calciferol SerPl-Imp
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or red-top clot activator tube; plasma acceptable in lithium heparin or EDTA tubes
- Units
- N/A
- Ref low
- 20
- Ref high
- 29
- Critical range
- 10 N/A – 100 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Immunoassay (CLIA/ECLIA) with narrative interpretive reporting
- CPT
- 82306
- SNOMED
- 4419008
- Specimen volume
- 1-2 mL of serum or plasma; minimum 0.5 mL
- Stability
- Room temperature: 8 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or lower): 6 months. Protect from light. Stable through 3 freeze/thaw cycles.
- Hemolysis max
- 100
- Lipemia max
- 300
- Icterus max
- 50
- TAT
- 24–72 hours
- Order
- routine
Why This Test Is 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 may also be used to monitor vitamin D levels in people taking vitamin D 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 needed. You may have a small needle inserted into a vein in your arm to draw blood. If you’re concerned about needles, let your healthcare provider know.
What the Results Mean
Results are typically reported as a concentration of vitamin D in the blood. While reference ranges can vary by lab, low levels may suggest deficiency, while very high levels may require further evaluation.
Common Reasons for Low or High Levels
Low levels of vitamin D can be caused by limited sun exposure, certain medical conditions (like malabsorption disorders), or medications. High levels may result from overuse of supplements or certain medical treatments.
Reference range
Interpretation-based report. Quantitative 25-OH vitamin D2 and D3 results are provided alongside clinical interpretation: Deficient (<20 ng/mL), Insufficient (20-29 ng/mL), Sufficient (≥30 ng/mL), and Potential Toxicity (>100 ng/mL). Reference ranges may vary by laboratory, assay platform, and population studied.N/A
No fasting required. Patient should inform clinician of all supplements, medications (especially anticonvulsants, corticosteroids, and vitamin D analogues), and recent sun exposure. Bariatric surgery patients and those with malabsorption syndromes should note relevant clinical history.
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?
How does vitamin D deficiency affect my health?
Can I prevent vitamin D deficiency?
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 15, 2026. · Read our editorial policy