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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 helps your body absorb calcium and maintain strong bones. Low levels may indicate deficiency, which can affect bone health and other body functions.

Quick summary

["Vitamin D levels help prevent deficiencies that can lead to health risks like bone weakness or muscle pain."]

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

Key facts at a glance

LOINC
10119-6
Short code
ST wave MD L-AVL
Synonyms
ST wave MD L-AVL
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 like fatigue, muscle weakness, or bone pain. It’s also used to check for vitamin D deficiency in people who don’t get enough sunlight, have limited sun exposure, or have certain medical conditions that affect vitamin D absorption.

What to Expect Before the Test

No special preparation is needed. You may have a blood draw from a vein in your arm. If you’re taking vitamin D supplements, let your provider know, as this can affect results.

What the Results Mean

Results are compared to a standard range for healthy adults. Low levels may mean you’re not getting enough vitamin D from diet or sunlight. High levels could indicate over-supplementation or other conditions.

Common Causes of Low or High Levels

Low levels may be due to limited sun exposure, poor diet, certain digestive disorders, or liver/kidney problems. High levels can result from overuse of supplements or rare genetic conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin D level

Frequently asked questions

Why did my doctor order this test?
Your doctor may have noticed symptoms like bone pain, fatigue, or muscle weakness, or they suspect a vitamin D deficiency based on your medical history or lifestyle.
What does a low vitamin D level mean?
A low level may mean your body isn’t getting enough vitamin D from sunlight, diet, or supplements. It can affect bone health and other body functions, so your doctor may recommend changes to your diet, sunlight exposure, or supplements.
Can I take vitamin D supplements without checking my levels first?
It’s best to check your vitamin D level first. Taking too much vitamin D can cause health issues like kidney problems or calcium buildup in organs. Always follow your doctor’s advice.
  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