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
4466-9
Short code
Vital Stn Smn
Synonyms
Vital Stn Smn
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 to check for vitamin D deficiency, especially if you have symptoms like fatigue, bone pain, or frequent infections. It’s also used to monitor vitamin D levels in people who take supplements or have conditions affecting vitamin D metabolism, such as kidney disease or limited sun exposure.

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, but this depends on your healthcare provider’s instructions. Wear comfortable clothing and plan to rest after the blood draw.

What Happens During the Test?

A healthcare professional will insert a small needle into your arm to draw a blood sample. You may feel a slight pinch, but the process usually takes just a few minutes. The blood is then sent to a lab for analysis.

What Are Possible Results?

Results are compared to a reference range, but exact values vary by lab. Low levels may suggest deficiency, while high levels could indicate over-supplementation or certain medical conditions. Your provider will discuss results with you in context of your health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Vitamin D Level

Frequently asked questions

What Does This Test Tell Us About My Health?
Low vitamin D levels may increase the risk of bone disorders (like osteoporosis), muscle weakness, or immune-related issues. High levels can sometimes signal kidney problems or vitamin D toxicity, though this is rare. Your provider will interpret results alongside your symptoms and other test results.
How Often Should I Get This Test?
Frequency depends on your health status. People with risk factors (e.g., limited sun exposure, kidney disease, or malabsorption disorders) may need testing every 6–12 months. Pregnant individuals or those with certain conditions may also require more frequent checks.
Can I Take Vitamin D Supplements Without Checking My Levels First?
It’s best to avoid high-dose supplements without checking your levels first. Vitamin D toxicity can occur with excessive intake, and your provider can guide you on safe dosing based on your test results.
  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