Skip to content

Vitamin D total concentration (serum/plasma)

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

This test measures the total amount of vitamin D in your blood, which helps your body absorb calcium and maintain strong bones.

Quick summary

["Vitamin D supports bone health and immune function; low levels may indicate deficiency."]

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

Key facts at a glance

LOINC
20948-6
Short code
Vit A Tiss-mCnt
Synonyms
Vit A Tiss-mCnt
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 like fatigue, muscle weakness, or bone pain, or if you’re at higher risk for vitamin D deficiency (e.g., limited sun exposure, certain medical conditions, or dietary habits). It’s also used to monitor vitamin D levels in people taking supplements or those with conditions like osteoporosis.

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 draw if your lab uses a specific method. Wear a comfortable shirt for easy access to your arm.

What Happens During the Test?

A healthcare professional will insert a small needle into your arm to draw blood. You may feel a brief pinch, but it’s quick. The blood is then sent to a lab for analysis.

What Are Possible Results?

Results are typically reported as a concentration of vitamin D in blood (units like ng/mL or nmol/L). Your provider will compare these to general reference ranges to assess your status.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low vitamin D levels may lead to weakened bones, muscle weakness, or increased risk of infections. High levels can sometimes cause nausea, headaches, or kidney issues. Your provider will interpret results in the context of your overall health and symptoms.

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 in fatty fish, fortified foods), certain medical conditions (e.g., malabsorption), or medications that interfere with its production or metabolism.
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 provider will contact you once they’re ready for review.
Can I take vitamin D supplements before the test?
If your provider prescribed supplements, you may need to stop them temporarily or follow specific timing instructions to avoid affecting test accuracy. Always check with your provider first.
  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