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Serum Vitamin D (25-Hydroxyvitamin D) by Immunoassay

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

This test measures your body’s level of vitamin D, an important nutrient that helps your bones stay strong and supports overall health.

Quick summary

["Vitamin D levels help assess your risk for deficiencies that may affect bone health or other health conditions."]

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

Key facts at a glance

LOINC
68406-8
Short code
Lymph Abn NFr Vitf Manual
Synonyms
Lymph Abn NFr Vitf Manual
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
manual-count
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 if you have symptoms of low vitamin D, such as fatigue, bone pain, or frequent infections. It’s also used to monitor vitamin D levels in people who take supplements or have conditions that affect vitamin D absorption, like celiac disease or Crohn’s disease.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample drawn from a vein in your arm. If you’re on blood thinners, let your doctor know before the test.

What the Results Mean

Results help determine if your vitamin D levels are sufficient, insufficient, or very low. Low levels may require dietary changes, supplements, or medical advice to address.

Common Reasons for Testing

Doctors test vitamin D levels to check for deficiencies, especially in people with limited sun exposure, darker skin, or certain health conditions that interfere with vitamin D production or absorption.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin D deficiency can lead to weakened bones (osteomalacia or rickets in children), increased risk of fractures, or weakened immune function. High levels may also cause symptoms like nausea or kidney stones, though this is rare.

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, poor diet (low in fatty fish or fortified foods), certain medications, or health conditions like malabsorption syndromes.
How long does it take to get results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time.
Can I take vitamin D supplements without checking my levels first?
It’s best to discuss supplement use with your doctor, especially if you have kidney disease or take other medications, to avoid potential risks like excess vitamin D.
  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