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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 absorb calcium and maintain bone health. Low levels may indicate deficiency, which can affect muscle strength, bone density, and overall health.

Quick summary

["Vitamin D levels help prevent deficiencies that could lead to health risks like bone weakness or muscle pain."]

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

Key facts at a glance

LOINC
22601-9
Short code
VZV IgG Titr CSF
Synonyms
VZV IgG Titr CSF
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Ref low
8
Ref high
61
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82977
SNOMED
3110003
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test if you have symptoms like fatigue, muscle weakness, bone pain, or if you’re at higher risk for vitamin D deficiency—such as not getting enough sunlight, having limited sun exposure, or having certain medical conditions (e.g., kidney or liver disease). It’s also used to monitor treatment for conditions like osteoporosis or rickets.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the blood draw if your lab uses a specific method. Wear comfortable clothing and plan to rest after the draw.

What Happens During the Test?

A healthcare provider will insert a small needle into a vein in your arm to collect blood. It usually takes a few minutes, and you may feel a brief pinch. The blood is then sent to a lab for analysis.

What Are the Results?

Results are typically reported as a numerical value (in ng/mL or nmol/L) representing your vitamin D level. Your doctor will interpret these results in relation to your symptoms, medical history, and other tests.

Reference range

Adult males: 8-61 U/L; Adult females: 5-36 U/LN/A

Specimen: csf

No special preparation required. Avoid fatty meals before the test if possible.

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 deficiency?
Vitamin D deficiency often results from limited sun exposure, poor diet (low intake of fatty fish, fortified foods), or conditions that impair vitamin D production or absorption (e.g., malabsorption syndromes, obesity). Rarely, genetic factors or certain medications may also contribute.
How long does it take to get results?
Results are usually available within 1–3 business days, depending on your lab’s processing time. Your doctor will contact you once they’re ready to discuss the findings.
Can I take vitamin D supplements before the test?
Yes, but avoid taking large doses (e.g., >4,000 IU/day) unless advised by your doctor. If you’re on supplements, check with your provider to ensure they don’t interfere with test accuracy or your treatment plan.
  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