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Vitamin D Level (25-Hydroxyvitamin D)

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.

Quick summary

Vitamin D levels help assess bone health and overall nutrient status.

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

Key facts at a glance

LOINC
64369-2
Short code
DIALYSISPATIENTSWHOHAVERECEIVEDORARERECEIVINGVOCATIONALREHABILITATIONS
Synonyms
—
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 Might Be Ordered

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 not getting enough sunlight, having limited sun exposure, or having certain medical conditions that affect vitamin absorption.

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., 25-hydroxyvitamin D). Bring any medications you’re currently taking to your appointment.

What Happens During the Test

A healthcare professional will draw blood from a vein in your arm. It typically takes a few minutes, and you may feel a slight pinch or discomfort. The blood sample is then sent to a lab for analysis.

What the Results Mean

Results are usually reported in nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L). Your provider will interpret the results in relation to your health status and any symptoms you have.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low vitamin D levels can contribute to conditions like osteoporosis, muscle weakness, or increased risk of certain infections. High levels may indicate over-supplementation or liver/kidney issues. Your provider will discuss findings in the context of your overall health.

Short name

Vitamin D Blood Test

Frequently asked questions

How long does it take to get my vitamin D test results?
Results are usually available within 1–3 business days, depending on your lab’s processing time. Your provider will contact you once they’re ready to review them with you.
Can I take vitamin D supplements before my blood test?
If your test involves a fasting requirement, avoid vitamin D supplements for 48 hours before the draw. If fasting isn’t required, discuss with your provider whether timing matters for your specific test.
What if my vitamin D level is low?
If your results show low levels, your provider may recommend dietary changes, increased sun exposure, or supplements under medical supervision to help restore healthy levels.
  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