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Serum Vitamin D (25-Hydroxyvitamin D) with Immunoassay Confirmation

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

This test measures your blood levels of vitamin D, an important nutrient that helps your body absorb calcium and maintain strong bones. Low levels may indicate deficiency, which can affect bone health and other body functions.

Quick summary

["Vitamin D levels help prevent deficiencies that could 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
13280-3
Short code
RUBV IgG sp2 Ser-aCnc
Synonyms
RUBV IgG sp2 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 This Test Is Done

Your doctor may order this test if you have symptoms like muscle weakness, bone pain, or frequent infections. It’s also used to check for vitamin D deficiency in people who don’t get enough sunlight, have limited sun exposure, or have certain medical conditions that affect vitamin D absorption.

What to Expect Before the Test

No special preparation is needed. You may be asked to fast for 8–12 hours before the blood draw, but this depends on your doctor’s instructions. Wear comfortable clothing and plan to rest after the blood sample is taken.

What Happens During the Test

A healthcare professional will insert a small needle into your arm to draw blood. You may feel a brief pinch, but it usually doesn’t cause pain. The blood is then sent to a lab for testing.

What the Results Mean

Results are compared to standard ranges to determine if your vitamin D levels are within a healthy range. Low levels may require supplements or lifestyle changes, while very high levels may need monitoring.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin D Level

Frequently asked questions

What causes vitamin D levels to be low?
Vitamin D deficiency can be caused by limited sun exposure, poor diet (low intake of fatty fish, fortified foods, or supplements), certain medical conditions (like celiac disease or malabsorption), or taking medications that interfere with its absorption.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab and insurance. Your doctor will contact you once they’re ready.
Can I take vitamin D supplements without checking my levels first?
It’s best to check your levels first. High doses of vitamin D can be harmful, and your doctor can guide you on safe supplementation based on your test results.
  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