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Vitamin D, 25-Hydroxy [ser/plas]

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

This test measures the level of vitamin D in your blood, which helps your body use calcium for strong bones and teeth. Low levels may indicate deficiency, which can affect muscle function and bone health.

Quick summary

["Vitamin D levels help assess bone health and overall nutrient status."]

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

Key facts at a glance

LOINC
10022-2
Short code
R' wave dur L-AVF
Synonyms
R' wave dur L-AVF
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 doctor may order this test to check if you have enough vitamin D, especially if you have symptoms like muscle weakness, fatigue, or bone pain. It’s also used to monitor conditions like osteoporosis or rickets, or to evaluate vitamin D supplements.

What Does a Low or High Level Mean?

Low levels might mean you’re not getting enough sunlight, have limited sun exposure, or have conditions that affect vitamin D absorption (e.g., kidney or liver disease). High levels can sometimes cause calcium buildup in organs, though this is rare.

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’s analyzed to measure vitamin D levels using a blood test method.

What Are Common Causes of Abnormal Results?

Factors like diet (low intake of fatty fish, fortified foods), sun exposure, obesity, or certain medications (like anticonvulsants) can affect vitamin D levels. Age also plays a role—older adults may produce less vitamin D naturally.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

25-Hydroxy Vitamin D

Frequently asked questions

What symptoms might I notice if my vitamin D is low?
Symptoms of low vitamin D can include fatigue, muscle pain or weakness, bone pain, or frequent infections. However, many people with deficiency don’t have noticeable symptoms until it’s severe.
How often should I get this test?
Your doctor will determine how often you need testing based on your health, age, and risk factors (e.g., limited sun exposure, certain medical conditions). Typically, it’s recommended for adults over 50 or those with known deficiencies.
Can I take supplements to boost my vitamin D?
Yes, vitamin D supplements (in forms like D2 or D3) can help if your levels are low. Always follow your doctor’s advice on dosage and avoid excessive supplements, as too much can be harmful.
  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