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Serum Vitamin D (25-Hydroxyvitamin D) Level

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

This test measures the amount of vitamin D in your blood, specifically the form called 25-hydroxyvitamin D, which is the active form your body uses to absorb calcium and maintain bone health.

Quick summary

["Vitamin D levels help assess your risk for bone-related conditions and overall health."]

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

Key facts at a glance

LOINC
69962-9
Short code
RSV IgM Ser Ql IA
Synonyms
RSV IgM Ser 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 This Test Matters

Vitamin D is essential for bone health, immune function, and muscle strength. Low levels may indicate deficiencies that can lead to conditions like osteoporosis, muscle weakness, or increased infection risk. Your doctor may recommend this test if you have symptoms like fatigue, bone pain, or if you’re at higher risk for deficiency (e.g., limited sun exposure, certain medical conditions).

How the Test Works

A small blood sample is taken from your arm, and the lab analyzes it using an immunoassay method to measure the specific form of vitamin D in your serum.

What to Expect Before the Test

No special preparation is needed, but you may want to drink plenty of water the day of your test. If you’re taking vitamin D supplements, let your healthcare provider know, as this may affect your results.

Possible Results and Interpretation

Results are typically reported in nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L). Your doctor will interpret the results in relation to your overall health and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin D Blood Test

Frequently asked questions

What are the normal ranges for this test?
Normal ranges can vary slightly depending on the lab and testing method. Generally, optimal vitamin D levels are considered to be between 30 and 50 ng/mL (75 to 125 pmol/L). Levels below this may indicate a deficiency, while levels above may suggest excess intake or other conditions.
Can vitamin D levels change over time?
Yes, vitamin D levels can fluctuate due to factors like sun exposure, diet, and seasonal changes. Regular monitoring may be recommended if you have ongoing health concerns or risk factors for deficiency.
What symptoms might indicate low vitamin D levels?
Symptoms of low vitamin D can include fatigue, muscle weakness or pain, bone pain, frequent infections, or mood changes. If you experience these symptoms, talk to your doctor about whether this test or other evaluations are needed.
  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