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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, immune function, and overall well-being. Low levels may indicate deficiency, which can affect these areas.

Quick summary

["Vitamin D levels help ensure your body has enough of this essential nutrient."]

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

Key facts at a glance

LOINC
10122-0
Short code
ST wave MD L-II
Synonyms
ST wave MD L-II
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ekg
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 pain, fatigue, or bone pain. It’s also used to monitor vitamin D levels in people at 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 needed. If you’re having blood drawn, you may want to drink plenty of fluids the day of the test to help reduce discomfort. Avoid smoking or drinking alcohol before the test if advised by your provider.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. The process is quick and typically painless. The blood sample is sent to a lab for analysis.

What Are the Possible Results?

Results are compared to standard reference ranges, though exact values may vary by lab. Low levels may indicate deficiency, while high levels could suggest over-supplementation or certain medical conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Vitamin D Level

Frequently asked questions

How long will it take to get my results?
Results are usually available within 1–3 business days, depending on your lab. Follow up with your provider to discuss the results and any next steps.
What does a low vitamin D level mean?
A low vitamin D level may mean you’re not getting enough from sunlight, diet, or supplements. It can affect bone health, muscle function, and immune support. Your provider may recommend changes in diet, sunlight exposure, or supplements.
Can I take vitamin D supplements without checking my levels first?
It’s best to check your levels first. Taking too much vitamin D can cause health issues like kidney problems. Always follow your provider’s advice on supplementation.
  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