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Serum or Plasma Mass 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 bone health. Low levels may indicate deficiency, while higher levels may signal overabsorption or other conditions.

Quick summary

["Vitamin D levels help assess bone health and potential deficiencies."]

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

Key facts at a glance

LOINC
3121-1
Short code
VMA SerPl-mCnc
Synonyms
VMA SerPl-mCnc
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 of vitamin D deficiency, such as muscle weakness, bone pain, or frequent infections. It may also be used to monitor vitamin D levels in people with conditions like osteoporosis, kidney disease, or those taking vitamin D supplements.

What Does a Low Level Mean?

Low levels of vitamin D can affect bone health, immune function, and muscle strength. Deficiency is common in people who don’t get enough sunlight, have limited sun exposure, or have certain medical conditions.

What Does a High Level Mean?

High levels of vitamin D can sometimes cause calcium buildup in the body, leading to symptoms like nausea, vomiting, or kidney stones. This is less common but requires monitoring.

How Is This Test Performed?

A blood sample is taken from a vein in your arm. The sample is sent to a lab, where it is analyzed to measure vitamin D levels using a specialized test method.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Vitamin D plays a critical role in bone metabolism, immune function, and overall health. Deficiency is associated with increased risk of fractures, infections, and certain chronic diseases. Regular monitoring helps manage conditions like rickets (in children) or osteomalacia (adult bone softening).

Short name

Vitamin D Level

Frequently asked questions

What are the normal ranges for vitamin D?
There is no single standard range for all adults, as levels can vary based on age, health status, and lab-specific methods. Your results will be interpreted by your healthcare provider in the context of your overall health.
How often should I get this test?
Your healthcare provider will determine how often you need this test based on your medical history, symptoms, and risk factors. Some people may need testing every few months, while others may only need it once a year.
Can vitamin D levels change quickly?
Yes, vitamin D levels can fluctuate due to changes in sun exposure, diet, or supplements. If you’ve recently changed your diet or started taking supplements, let your provider know so they can adjust recommendations accordingly.
  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