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Serum/plasma concentration of vitamin D (25-hydroxyvitamin D)

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.

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
8798-1
Short code
RV SVI Spiral CT
Synonyms
RV SVI Spiral CT
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ct-spiral
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 (e.g., limited sun exposure, certain dietary habits, or conditions like osteoporosis). It’s also used to monitor treatment for deficiencies or excesses.

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 blood draw if your test involves a specific timing (e.g., 24-hour samples). Wear comfortable clothing and arrange for someone to drive you home if needed.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but it’s usually over quickly. The blood sample is sent to a lab for analysis.

What Are the Results Measured Against?

Results are compared to standard ranges for vitamin D concentration in the blood, though individual ranges may vary slightly by lab. Your provider will interpret results in the context of your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin D Level

Frequently asked questions

How long does it take to get my results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Follow up with your provider to discuss the findings.
What causes vitamin D deficiency?
Deficiency can result from limited sun exposure, poor diet (low intake of fatty fish, fortified foods, or supplements), certain medications, or conditions that affect vitamin D absorption or metabolism.
Can I take vitamin D supplements without checking my levels first?
It’s best to consult your healthcare provider before starting supplements. They can guide you based on your test results and overall health to avoid excess.
  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