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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 is important for bone health and other bodily functions. Low levels may indicate deficiency, while higher levels could signal excess intake or certain conditions.

Quick summary

["Vitamin D levels help assess your risk for bone-related issues and overall health."]

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

Key facts at a glance

LOINC
51458-8
Short code
HDV IgG Ser-aCnc
Synonyms
HDV IgG Ser-aCnc
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 of vitamin D deficiency, such as muscle weakness, bone pain, or frequent infections. It may also be recommended for people at higher risk, like those with limited sun exposure, certain medical conditions, or those taking medications that affect vitamin D absorption.

What to Expect Before the Test

No special preparation is usually needed. If you’re having blood drawn, you may want to drink plenty of fluids the day of the test to help reduce discomfort. If you’re having a urine test, follow any specific instructions your provider gives you.

What Happens During the Test?

For a blood test, a small needle will be used to draw blood from a vein in your arm. For a urine test, you may collect a sample over a 24-hour period or provide a single sample depending on the instructions. The sample is then sent to a lab for analysis.

What Are the Possible Results?

Results are typically reported as a concentration of vitamin D in the blood (e.g., nanograms per milliliter or picograms per milliliter). Your provider will interpret the results in relation to your health and symptoms. Normal ranges can vary slightly between labs.

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 can result from limited sun exposure, poor diet (low intake of fatty fish, fortified foods, or supplements), certain medical conditions (like malabsorption disorders), or taking medications that interfere with vitamin D metabolism.
How can I improve my vitamin D levels?
To support healthy vitamin D levels, get regular sunlight exposure (as recommended by your provider), eat foods rich in vitamin D (like salmon, eggs, and fortified dairy), and consider supplements if advised by your healthcare team. Always follow their guidance on dosage.
Is there anything I should avoid before the test?
Generally, no specific restrictions apply, but avoid heavy exercise or stress before blood draws to help reduce anxiety. If you’re taking medications that affect vitamin D, let your provider know before the test.
  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