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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, a fat-soluble nutrient essential for bone health and other functions.

Quick summary

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

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

Key facts at a glance

LOINC
14307-3
Short code
VZV IgG sp2 Ser IA-aCnc
Synonyms
VZV IgG sp2 Ser IA-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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 doctor may order this test to check if you have enough vitamin D, which is important for preventing conditions like osteoporosis or rickets. It can also help diagnose deficiencies that may cause symptoms like fatigue, muscle weakness, or bone pain. Some people are at higher risk of deficiency due to limited sun exposure, certain medical conditions, or dietary habits.

What to Expect Before the Test

No special preparation is needed for this blood test. You may be asked to fast for 8–12 hours before the draw if your lab uses a specific method, but this is rare for vitamin D testing. Bring your test results or questions to your appointment.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. You may feel a slight pinch, but the process is quick. The blood is then sent to a lab for analysis.

What Are Possible Results?

Results are reported as a concentration of vitamin D in the blood (typically measured in nanograms per milliliter, or ng/mL). Your doctor will interpret the results based on your health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin D level

Frequently asked questions

What does a low vitamin D level mean?
A low vitamin D level may mean your body isn’t getting enough from sunlight, diet, or absorption. Symptoms could include fatigue, muscle pain, or frequent infections. Your doctor may recommend lifestyle changes, supplements, or further testing.
How long does it take to get results?
Results are usually available within 1–3 business days, depending on your lab. Your doctor will contact you once they’re ready.
Can I take vitamin D supplements without checking my levels first?
It’s best to check your vitamin D level first. Taking too much can cause health issues like calcium problems. Always follow your doctor’s advice.
  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