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Vitamin D, 25-Hydroxy [Serum]

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of vitamin D in your blood to check if you have enough of this important nutrient, which 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 17, 2026Editorial policy

Key facts at a glance

LOINC
61544-3
Short code
How much vitamin E PhenX
Synonyms
How much vitamin E PhenX
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
5
Ref high
20
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
phenx
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 may have a small needle inserted into your arm to draw blood. If you’re taking blood from your own vein at home, follow your healthcare provider’s instructions carefully.

What the Results Mean

Results help determine if your vitamin D levels are within a healthy range. Low levels may indicate a need for supplements or lifestyle changes to improve intake.

Common Causes of Abnormal Results

Low vitamin D levels can be due to insufficient sun exposure, poor diet, certain medications, or medical conditions affecting absorption. High levels may suggest over-supplementation or rare metabolic issues.

Reference range

NCBI: Vitamin E 5-20 µg/mLN/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

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?
A vitamin D test may be ordered if you have symptoms like fatigue, bone pain, or if your doctor suspects you’re not getting enough vitamin D from diet or sunlight.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time and your healthcare provider’s follow-up schedule.
Can I take vitamin D supplements before the test?
Yes, but inform your healthcare provider beforehand if you’re taking supplements, as it may affect 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 17, 2026. · Read our editorial policy