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Serum Vitamin D (25-Hydroxyvitamin D) 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, which can affect bone strength and overall health.

Quick summary

["Vitamin D levels help prevent deficiencies that can lead to bone problems or other health risks."]

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

Key facts at a glance

LOINC
7992-1
Short code
RSV IgM Ser-aCnc
Synonyms
RSV IgM Ser-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 Is This Test Done?

Your healthcare provider may order this test if you have symptoms like muscle weakness, bone pain, or if you’re at higher risk for vitamin D deficiency, such as living far from the equator, having limited sun exposure, or having certain medical conditions.

What to Expect Before the Test

No special preparation is needed. You may have a blood sample drawn from a vein in your arm, similar to other blood tests. You can eat and drink normally before the test.

How the Test Works

The test measures the concentration of 25-hydroxyvitamin D, a form of vitamin D found in your blood. This is considered the most reliable way to assess your vitamin D status.

What the Results Mean

Results are typically reported in nanograms per deciliter (ng/dL) or picomoles per liter (pmol/L). Your healthcare provider will interpret the results in relation to your health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin D deficiency can lead to weakened bones, muscle weakness, fatigue, or increased risk of certain conditions like osteoporosis or certain cancers. Proper levels support immune function, muscle health, and overall well-being.

Short name

Vitamin D Level

Frequently asked questions

What causes low vitamin D levels?
Low vitamin D levels can be caused by limited sun exposure, certain medical conditions (like malabsorption disorders), obesity, or taking certain medications. Lifestyle factors, such as avoiding sun exposure or poor diet, also play a role.
How long does it take to correct vitamin D deficiency?
Treatment usually involves vitamin D supplements or increased sun exposure. The time to correct deficiency depends on the severity and your response to treatment, which your doctor will monitor.
Can vitamin D levels change quickly?
Yes, vitamin D levels can fluctuate due to changes in sun exposure, diet, or health conditions. Regular monitoring is recommended for those at risk or with known deficiencies.
  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