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Vitamin D, 25-Hydroxy [ser]

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

This test measures the amount of vitamin D in your blood, specifically the form called 25-hydroxyvitamin D, which reflects your overall vitamin D status.

Quick summary

["Vitamin D is essential for 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
43840-8
Short code
FLUBV IgM Ser Ql
Synonyms
FLUBV IgM Ser Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
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 This Test Matters

Vitamin D is crucial for maintaining strong bones by helping your body absorb calcium. It also plays a role in supporting immune function and may influence other health processes. Low levels of vitamin D can lead to conditions like osteoporosis, muscle weakness, or increased susceptibility to infections.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood, similar to other routine blood tests. If you’re on certain medications that affect vitamin D metabolism, your healthcare provider may advise adjustments.

What the Results Mean

Your results will show the concentration of 25-hydroxyvitamin D in your blood. While reference ranges vary by lab, levels below a certain threshold (often considered deficient) may prompt further evaluation or treatment recommendations.

Common Reasons for Testing

Doctors may order this test if you have symptoms like fatigue, bone pain, frequent infections, or if you’re at higher risk for vitamin D deficiency (e.g., limited sun exposure, certain medical conditions, or dietary restrictions).

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Vitamin D Level

Frequently asked questions

How often should I get this test?
Vitamin D levels can change over time due to factors like sun exposure, diet, or aging. Your healthcare provider may recommend testing every few years or more frequently if you have risk factors or symptoms. Follow their guidance based on your individual health needs.
What if my results are low?
If your vitamin D levels are low, your doctor may suggest lifestyle changes (like more sun exposure or dietary adjustments) or supplements to help raise your levels safely. They’ll work with you to determine the best approach for your situation.
Can vitamin D levels be affected by other medications?
Yes, some medications (like anticonvulsants, certain antibiotics, or steroids) can interfere with vitamin D metabolism or absorption. If you’re taking these or other medications, let your doctor know so they can consider how they might impact your 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