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Vitamin D, 25-Hydroxy [Mass concentration in serum]

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 strong bones. Low levels may indicate deficiency, affecting bone health or other health conditions.

Quick summary

["Vitamin D levels help prevent deficiencies that can 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
14529-2
Short code
RUBV Ag Cvx Ql IF
Synonyms
RUBV 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 bone pain, muscle weakness, 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.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, typically drawn from your arm. If you’re on blood thinners, let your provider know before the test.

What the Results Mean

Results are compared to standard ranges, but exact values can vary by lab. Low levels may require supplements or lifestyle changes, while very high levels might need monitoring.

Common Causes of Low or High Levels

Low levels can result from limited sun exposure, poor diet, certain medications, or liver/kidney issues. High levels may stem from overuse of supplements or certain medical treatments.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin D Level

Frequently asked questions

What triggers a vitamin D test?
Symptoms like bone pain, fatigue, or frequent illnesses, or if your doctor suspects deficiency based on your medical history or risk factors.
How long does it take to get results?
Results are usually available within 1–3 business days, depending on your lab.
Can I take vitamin D supplements before the test?
Yes, but inform your provider about any supplements you’re taking, as they may affect test accuracy.
  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