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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 level of vitamin D in your blood, which is important for bone health and overall well-being.

Quick summary

["Vitamin D levels help ensure your body has enough of this essential nutrient."]

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

Key facts at a glance

LOINC
110975-0
Short code
LASV IgG Msmt Ser
Synonyms
LASV IgG 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 This Test Matters

Vitamin D is crucial for maintaining strong bones and supporting immune function. Low levels may indicate deficiencies that could affect your health, especially if you 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 test if it’s part of a comprehensive metabolic panel. Bring any medications you’re currently taking, as some may affect results.

What the Results Mean

Results are typically reported in nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L). Your healthcare provider will interpret the results in relation to your health status and symptoms.

Common Reasons for Testing

Doctors may order this test if you have symptoms like fatigue, muscle weakness, bone pain, or frequent infections. It’s also used to screen for vitamin D deficiency in high-risk groups, such as older adults, those with limited sun exposure, or individuals with certain medical conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

25-Hydroxy Vitamin D

Frequently asked questions

How long does it take to get my vitamin D test results?
Results are usually available within 1–3 business days, depending on your lab’s processing time. Follow up with your healthcare provider to discuss the findings and any next steps.
Can I take supplements before my vitamin D test?
If your doctor prescribed vitamin D supplements, wait at least 2 weeks after stopping them before retesting to avoid misleading results. If you’re unsure, ask your provider for guidance.
What if my vitamin D level is low?
If your results show low levels, your doctor may recommend dietary changes, increased sun exposure, or supplements to restore balance. They’ll work with you to create a plan tailored to 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