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Vitamin D, 25-Hydroxy [Serum]

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

This test measures the amount of vitamin D in your blood, which is important for bone health and overall well-being. Low levels may indicate deficiency, which can affect muscle function and immune health.

Quick summary

["Vitamin D levels help assess bone health and prevent deficiencies that may cause fatigue or muscle weakness."]

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

Key facts at a glance

LOINC
14553-2
Short code
MuV Ag UrnS Ql IF
Synonyms
MuV Ag UrnS Ql IF
Category
chemistry
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
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 frequent illnesses. It’s also used to check for vitamin D deficiency in people who don’t get enough sunlight or have limited exposure to vitamin D-rich foods.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the blood draw if your lab uses a specific method. Wear a comfortable shirt and bring your medical records if you have questions about prior results.

What Happens During the Test?

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

What Are Possible Results?

Results are typically reported in nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L). Your provider will interpret the results based on your health status 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 usually available within 1–3 business days, depending on your lab’s processing time. Your provider will contact you once they’re ready to discuss them.
What causes vitamin D deficiency?
Deficiency often results from limited sun exposure, poor diet (low intake of fatty fish, fortified foods), or conditions that affect vitamin D absorption (e.g., celiac disease, kidney/liver disorders).
Can I take supplements to raise my vitamin D levels?
Yes, supplements (vitamin D3 is most effective) can help, but your provider may recommend a specific dose based on your test results. Overdoing supplements can also cause harm, so follow their guidance.
  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