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Serum/plasma Vitamin D (25-hydroxy) concentration

Published: August 9, 2026Updated: August 16, 2026

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 deficiency, affecting muscle function and bone density.

Quick summary

["Vitamin D deficiency can lead to weakened bones, muscle pain, or fatigue—get tested if you suspect low levels."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
95707-6
Short code
MAYV IgA Spec Ql IA
Synonyms
MAYV IgA Spec Ql IA
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
CPT
82784
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 Vitamin D Matters

Vitamin D is essential for bone health, immune function, and muscle strength. Your body produces some vitamin D from sunlight, but diet and supplements can also contribute. This test checks if your levels are within a healthy range.

What the Test Measures

The test detects 25-hydroxyvitamin D, a form of vitamin D found in your blood. It’s the best indicator of your overall vitamin D status, as other forms (like 1,25-dihydroxyvitamin D) are produced in smaller amounts.

Common Causes of Low or High Levels

Low levels may result from limited sun exposure, certain medical conditions (e.g., malabsorption), or medications. High levels could be due to overuse of supplements or rare genetic disorders.

What to Expect Before the Test

No special preparation is needed, but tell your provider about any supplements (like vitamin D or calcium) you’re taking. A blood sample is drawn from a vein, usually in your arm.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Vitamin D Level

Frequently asked questions

Is vitamin D deficiency common?
Yes, about 40% of adults in the U.S. have insufficient or deficient vitamin D levels, especially those with limited sun exposure or darker skin tones. Deficiency can increase risks for osteoporosis, infections, and certain chronic diseases.
How often should I get this test?
Most adults should get tested every 1–2 years, especially if you have risk factors (e.g., limited sun exposure, obesity, or a history of bone problems). Your provider may recommend more frequent testing if you’re at higher risk.
Can I take vitamin D supplements without testing?
No, supplements should be taken under medical supervision. High doses can cause toxicity, and testing ensures your levels stay safe and effective.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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