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

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

This test measures your body’s level of vitamin D, which is important for bone health and other functions.

Quick summary

["Vitamin D helps keep bones strong and supports immune function."]

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

Key facts at a glance

LOINC
31889-9
Short code
MuV Ag Cvx Ql
Synonyms
MuV Ag Cvx Ql
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 doctor may order this test to check if you have enough vitamin D, which can be low due to limited sun exposure, certain medical conditions, or poor diet. It’s also used to monitor vitamin D levels if you’re taking supplements or have conditions like osteoporosis or rickets.

What Does a Low or High Level Mean?

Low levels may indicate conditions like rickets (in children), osteoporosis, or muscle weakness. High levels can sometimes cause nausea, headaches, or kidney problems, though this is rare.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm. The blood is sent to a lab where it’s analyzed to measure vitamin D levels using a specialized immunoassay method.

What Should You Do Before the Test?

No special preparation is needed, but let your doctor know if you’re taking vitamin D supplements or have any conditions that might affect results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin D level

Frequently asked questions

What causes vitamin D levels to be low?
Low vitamin D levels can result from limited sun exposure, certain medications, malabsorption issues (like celiac disease or Crohn’s), obesity, or liver/kidney problems.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time.
Can vitamin D levels change quickly?
Yes, vitamin D levels can fluctuate based on sun exposure, diet, and supplements. Regular monitoring may be needed if you have ongoing health concerns.
  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