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Vitamin D (25-hydroxy) with mass concentration measurement in serum/plasma

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

This test measures your blood levels of vitamin D, a crucial nutrient for bone health, immune function, and overall well-being. Low levels may indicate deficiency, which can affect your body’s ability to absorb calcium and maintain strong bones.

Quick summary

["Vitamin D levels help assess your risk for deficiency and guide treatment if needed."]

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

Key facts at a glance

LOINC
1624-6
Short code
Vit A 3h p 5000 U SerPl-mCnc
Synonyms
Vit A 3h p 5000 U SerPl-mCnc
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 Is This Test Done?

Your healthcare provider may order this test if you have symptoms of vitamin D deficiency, such as muscle weakness, bone pain, or frequent infections. It’s also recommended for people at higher risk, like those with limited sun exposure, certain medical conditions, or those who don’t consume enough 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 fasting protocols. Wear comfortable clothing and plan to stay near the testing site for a short time.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but the procedure is quick. The blood sample will be sent to a lab for analysis to measure vitamin D levels.

What Are the Results?

Results will show your vitamin D concentration in mass units per mass (e.g., ng/mL or nmol/L). Your provider will interpret these results in the context of your health and symptoms to determine if you need further action.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Vitamin D Level

Frequently asked questions

What Does a Low Level Mean?
Low vitamin D levels may indicate deficiency, which can lead to weakened bones, increased infection risk, or other health issues. Your provider may recommend supplements or lifestyle changes to improve levels.
What Does a High Level Mean?
High levels can sometimes indicate over-supplementation or certain medical conditions. Your provider will review your results with you to check for any concerns.
How Often Should I Get This Test?
Your provider will decide how often to check your vitamin D levels based on your health status, risk factors, and treatment plan. Regular monitoring may be recommended if you have ongoing health conditions or take supplements.
  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