Vitamin D (25-hydroxy) Serum Mass Concentration
This test measures the amount of vitamin D in your blood, specifically the form called 25-hydroxyvitamin D, which your body uses to assess overall vitamin D levels.
["Vitamin D is important for bone health and immune function; low levels may indicate deficiency."]
Key facts at a glance
- LOINC
- 1991-9
- Short code
- VDBP
- Synonyms
- Calciferol BP Ser-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum Separator Tube (SST, tiger-top) or Red-Top Vacutainer tube
- Units
- N/A
- Ref low
- 4
- Ref high
- 10
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- Enzyme-Linked Immunosorbent Assay (ELISA) or Radial Immunodiffusion (RID); commonly measured by immunonephelometry or chemiluminescence immunoassay (CLIA)
- CPT
- 86332
- SNOMED
- 39579001
- Specimen volume
- 1.0-2.0 mL of serum (minimum 0.5 mL)
- Stability
- Room temperature: 8 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 6 months. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 50
- Lipemia max
- 100
- Icterus max
- 25
- TAT
- 24–96 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 fatigue, bone pain, or frequent infections—or if you’re at higher risk, like having limited sun exposure, certain medical conditions, or dietary restrictions. It’s also used to monitor vitamin D levels after treatment for deficiency.
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 fasting protocol. Wear comfortable clothing and plan to spend 15–30 minutes at the testing site.
What Happens During the Test
A healthcare professional will insert a small needle into a vein in your arm to draw blood. You may feel a brief pinch, but the procedure usually takes only a few minutes. The blood sample is then sent to a lab for analysis.
What the Results Mean
Results are reported as a mass concentration of vitamin D in nanograms per milliliter (ng/mL). Your provider will interpret the results in relation to your symptoms, medical history, and other factors.
Reference range
Adults: 4.0-10.0 mg/L (400-1000 mg/dL); values may vary by methodology and laboratory. Pediatric and pregnancy reference ranges may differ.N/A
No special patient preparation is required. Fasting is not necessary. Patients should inform their healthcare provider about any vitamin D supplementation or medications that may affect results.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low vitamin D levels can weaken bones, increase infection risk, and may contribute to conditions like osteoporosis, muscle weakness, or certain autoimmune diseases. High levels may indicate over-supplementation or liver/kidney issues. Your provider will discuss results in the context of your health.
Short name
Vitamin D Blood Test
Frequently asked questions
How long does it take to get my results?
What if my results are low?
Does this test require fasting?
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