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Serum or plasma concentration of vitamin D (25-hydroxyvitamin D)

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 other body functions.

Quick summary

["Vitamin D helps maintain strong bones and supports immune function; low levels may indicate deficiency."]

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

Key facts at a glance

LOINC
94833-1
Short code
VZV DNA Amn NAA+probe-Log#
Synonyms
VZV DNA Amn NAA+probe-Log#
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-amp-tar
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test to check if you have enough vitamin D, especially if you have symptoms like muscle weakness, bone pain, or if you don’t get enough sunlight. It’s also used to monitor vitamin D levels in people with conditions like osteoporosis or kidney disease.

What to Expect Before the Test

No special preparation is needed. You may have blood drawn from a vein in your arm, or if testing urine, you might need to collect a sample at home. If testing saliva, follow any instructions provided by your lab.

What the Results Mean

Results help determine if your vitamin D levels are within a healthy range. Low levels may need supplements or dietary changes, while very high levels could require medical attention to prevent health risks.

Common Causes of Abnormal Results

Low vitamin D levels can result from limited sun exposure, poor diet, certain medical conditions (like malabsorption), or medications. High levels may occur from over-supplementation or rare genetic disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin D deficiency is linked to weakened bones, increased infection risk, and other health issues. Regular monitoring helps manage conditions like rickets in children or osteoporosis in adults.

Short name

Vitamin D level

Frequently asked questions

How long does it take to get my results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Follow-up with your doctor if you have questions about your specific results.
Can I eat or drink anything before this test?
For blood tests, you can eat and drink normally unless instructed otherwise. For urine or saliva tests, check with your lab for any specific guidelines.
What if my vitamin D level is too low?
If your levels are low, your doctor may recommend vitamin D supplements (in pill or liquid form) or dietary changes. They’ll work with you to find the best plan for your needs.
  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