Your Laboratory Test: What It Is, Why It Is Done, and What Your Results Mean
This test measures the level of 25-hydroxyvitamin D3 in a small blood sample from your fingertip to check your vitamin D status.
{"Measures vitamin D level using a small finger-prick blood sample","Helps detect vitamin D deficiency or excess in the body","Important for evaluating bone health, calcium absorption, and immune function","Results guide supplementation and treatment decisions","Fast and simple test that can be done in clinic or at home"}
Key facts at a glance
- LOINC
- 95594-8
- Short code
- 25-OH D3 Cap
- Synonyms
- 25(OH)D3 BldC-mCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Capillary blood collection device (microtainer) with appropriate anticoagulant (EDTA or heparin) or serum separator
- Units
- N/A
- Ref low
- 30
- Ref high
- 100
- Critical range
- 10 N/A – 150 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Liquid chromatography-tandem mass spectrometry (LC-MS/MS)
- CPT
- 82306
- SNOMED
- 371371003
- Specimen volume
- Minimum 100-200 μL of capillary whole blood
- Stability
- Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days. Protect from light.
- Hemolysis max
- 50
- Lipemia max
- 50
- Icterus max
- 20
- TAT
- 24–72 hours
- Order
- routine
This test is a laboratory analysis performed on a sample collected from your body, such as blood, urine, or tissue. It measures specific substances or markers that show how well your organs and body systems are functioning and helps your doctor evaluate your overall health.
The 25-hydroxyvitamin D3 test measures the amount of 25-hydroxyvitamin D (also called calcidiol) in your blood. This form of vitamin D is the major circulating form in the body and is considered the best indicator of your overall vitamin D status. The test uses a small sample of capillary blood (whole blood from a fingertip prick).
Your healthcare provider may order this test to help diagnose a medical condition, monitor an illness you already have, check how well a treatment is working, or screen for potential health problems before symptoms appear. The results play an important role in guiding decisions about your care.
This test is ordered to: (1) screen for vitamin D deficiency, especially in people at risk such as older adults, those with limited sun exposure, or people with certain digestive conditions; (2) monitor vitamin D levels in patients taking vitamin D supplements; (3) help diagnose conditions related to calcium metabolism like rickets or osteomalacia; and (4) evaluate causes of abnormal calcium levels.
A trained healthcare professional will collect a small sample, usually by drawing blood from a vein in your arm with a sterile needle or by asking you to provide a urine specimen. The sample is then sent to a laboratory for analysis, and the collection itself typically takes only a few minutes.
A healthcare professional will clean your fingertip with an antiseptic wipe and use a small lancet to prick your finger. A few drops of blood are collected into a small container or test strip. The sample is then sent to a laboratory for analysis. The procedure is quick and causes minimal discomfort.
Your report will show your values, often alongside a reference range that represents results typical for healthy individuals. A value outside that range does not always mean you are ill, since factors such as age, medications, and diet can affect results. Always review your results with your healthcare provider, who can explain what they mean for your specific situation.
Results are typically reported in ng/mL or nmol/L. Generally: ≥30 ng/mL (≥75 nmol/L) is considered sufficient; 20-29 ng/mL (50-74 nmol/L) indicates insufficiency; and <20 ng/mL (<50 nmol/L) suggests deficiency. Your healthcare provider will interpret your results based on your overall health and risk factors.
Reference range
Sufficient: 30-100 ng/mL (75-250 nmol/L); Insufficient: 20-29 ng/mL (50-72 nmol/L); Deficient: <20 ng/mL (<50 nmol/L); Toxic: >100 ng/mL (>250 nmol/L)N/A
No fasting required. Collect capillary blood using proper microcollection techniques. Ensure adequate warming of puncture site to promote blood flow. Avoid excessive squeezing of fingertip which may contaminate sample with tissue fluid.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Vitamin D is essential for calcium absorption and bone health. Deficiency can lead to rickets in children and osteomalacia or osteoporosis in adults. Low vitamin D levels have also been associated with increased risk of infections, autoimmune diseases, and certain cancers. This test helps healthcare providers diagnose vitamin D-related disorders, guide supplementation therapy, and monitor treatment effectiveness.
Frequently asked questions
Do I need to fast before this test?
How long does it take to get results?
What can cause low vitamin D levels?
Can I take vitamin D supplements before the test?
What happens if my vitamin D is too high?
Sources
- 1
- 2Mayo Clinic - Vitamin DSource
- 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 10, 2026. · Read our editorial policy