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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 helps your body use calcium and maintain strong bones. Low levels may indicate deficiency, affecting bone health or other health conditions.

Quick summary

["Vitamin D levels help assess bone health and prevent deficiency-related issues."]

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

Key facts at a glance

LOINC
110998-2
Short code
WNV IgM Msmt Ser
Synonyms
WNV IgM Msmt Ser
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
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 muscle weakness, bone pain, or if you’re at higher risk for vitamin D deficiency (e.g., limited sun exposure, certain medical conditions, or dietary restrictions). It’s also used to monitor vitamin D levels in people taking supplements.

What to Expect Before the Test

No special preparation is needed. You may fast before the test if instructed, but your provider will confirm. Bring any medications or supplements you’re taking, as they can affect results.

How the Test Works

A blood sample is drawn from a vein in your arm. The lab analyzes the serum or plasma to measure vitamin D levels using an immunoassay method, which detects specific vitamin D molecules in your blood.

What the Results Mean

Results are compared to standard ranges, but exact values can vary by lab. Low levels may signal deficiency, while higher levels might indicate over-supplementation or other conditions. Your provider will interpret results in the context of your health history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin D level (25-OH)

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. Follow-up with your provider to discuss findings and next steps.
Can I take vitamin D supplements before the test?
Yes, but inform your provider if you’re taking supplements. They may adjust timing or interpretation of results to avoid interference.
What if my results are outside the normal range?
If your levels are low, your provider may recommend lifestyle changes (e.g., more sun exposure, diet) or supplements under medical supervision. If high, they may investigate causes like over-supplementation or kidney issues.
  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