Serum or plasma concentration of vitamin D (25-hydroxyvitamin D)
This test measures your body’s level of vitamin D, an important nutrient that helps your bones stay strong and supports overall health. Low levels may affect muscle function, bone health, and immune function.
["Vitamin D helps your body absorb calcium and maintain bone health; low levels may increase risk of fractures or deficiencies."]
Key facts at a glance
- LOINC
- 104688-7
- Short code
- MMR & VZV pnl SerPl
- Synonyms
- MMR & VZV pnl SerPl
- 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 to check for vitamin D deficiency, especially if you have symptoms like muscle weakness, fatigue, or bone pain. It’s also used in people with conditions like osteoporosis, kidney disease, or those who don’t get enough sunlight. Some tests may be done to monitor vitamin D levels after treatment for deficiency.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it’s a blood draw. Wear loose clothing and bring any medications you’re currently taking. If you’re pregnant or breastfeeding, let your provider know.
What Happens During the Test?
A healthcare professional will draw blood from a vein in your arm. The process is quick and typically painless, though you might feel a slight pinch. The blood is sent to a lab for analysis.
What Are Possible Results?
Results are reported as a concentration of vitamin D in the blood (measured in nanograms per milliliter, or ng/mL). Your provider will interpret the results based on your health history and symptoms. Very low levels may indicate deficiency, while very high levels may require further evaluation.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Vitamin D deficiency is common and can lead to serious health issues, including weakened bones, muscle pain, fatigue, or even increased risk of certain diseases. Regular monitoring is important for people at higher risk, such as those with limited sun exposure, darker skin, or certain medical conditions. High levels may signal over-supplementation or other underlying health concerns.
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 if my levels are low?
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