Vitamin D, 25-Hydroxy (Total) - Serum
This blood test measures the total amount of vitamin D in your body, which is important for bone health and immune function.
["Vitamin D levels help ensure your bones stay strong and support overall health."]
Key facts at a glance
- LOINC
- 31965-7
- Short code
- RUBV Ag Urth Ql
- Synonyms
- RUBV Ag Urth 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, such as not getting enough sunlight or having limited sun exposure. It’s also used to monitor vitamin D levels in people with conditions like osteoporosis or certain chronic illnesses.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the blood draw if your lab requires it. Wear comfortable clothing and plan to stay near the testing site for about 15 minutes while the sample is collected.
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 slight pinch, but it usually doesn’t cause discomfort. The blood sample is then sent to a lab for analysis.
What Are the Results Measured Against?
Results are compared to standard ranges for healthy adults, but your specific reference range may vary based on your age, sex, and health status. Your provider will discuss what your results mean in the context of your health.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low vitamin D levels can lead to weakened bones, muscle weakness, fatigue, or increased risk of certain illnesses. High levels may indicate over-supplementation or other underlying conditions. Regular monitoring is important for those with chronic health conditions or limited sun exposure.
Short name
Total 25-Hydroxy Vitamin D
Frequently asked questions
How long does it take to get my results?
What does a low vitamin D level mean?
Can I take vitamin D supplements without checking my levels first?
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