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Vitamin D, 25-Hydroxy [Mass Concentration]

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

This blood test measures the amount of vitamin D in your body, which is important for bone health and overall well-being.

Quick summary

["Vitamin D helps keep bones strong and supports immune function."]

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

Key facts at a glance

LOINC
14551-6
Short code
MuV Ag Cvx Ql IF
Synonyms
MuV Ag Cvx Ql IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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 risk for vitamin D deficiency, such as living far from the equator, having limited sun exposure, or having certain medical conditions that affect vitamin D absorption.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the blood draw, but this isn’t always required. Wear comfortable clothing and plan to stay near the testing site for about 15 minutes.

What Happens During the Test?

A healthcare professional will insert a small needle into your arm to draw blood. You may feel a slight sting, but it usually doesn’t cause significant discomfort. The blood will be sent to a lab for analysis.

What Do the Results Mean?

Results are compared to general reference ranges, but your specific needs may influence interpretation. Low levels may indicate deficiency, while higher levels could be due to supplements or other factors. Your provider will discuss findings with you.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin D plays a critical role in bone health, immune function, and muscle strength. Low levels can lead to conditions like rickets (in children) or osteomalacia (in adults), while very high levels may cause calcium-related issues. Regular monitoring is important for those at risk or with known deficiencies.

Short name

Vitamin D Level

Frequently asked questions

What causes vitamin D deficiency?
Vitamin D deficiency can result from limited sun exposure, poor diet (low intake of fatty fish, fortified foods), certain medical conditions (like celiac disease or kidney/liver disorders), or 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’s processing time. Your provider will contact you once they’re ready for discussion.
Can I take vitamin D supplements before the test?
It’s best to avoid taking vitamin D supplements 2–3 days before the test unless instructed otherwise by your provider, as this could affect the accuracy of your 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