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Serum/Plasma Substance Concentration (Mass) – Vitamin D (25-Hydroxy)

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

This test measures the level of vitamin D in your blood, specifically the active form that your body uses to maintain bone health and support immune function.

Quick summary

["Vitamin D levels help ensure proper 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
14550-8
Short code
MuV Ag Spt Ql IF
Synonyms
MuV Ag Spt Ql IF
Category
chemistry
Sample
sputum
Container
Sterile sputum container
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
CPT
85610
SNOMED
396252006
Specimen volume
3-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like fatigue, muscle weakness, bone pain, or if you’re at higher risk for vitamin D deficiency (e.g., limited sun exposure, certain dietary habits, or conditions like obesity or kidney disease). It may also be part of routine check-ups for adults over 50 or those with chronic illnesses.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if your lab uses a fasting protocol for vitamin D testing. Wear comfortable clothing and bring any medications or supplements you’re currently taking.

What Happens During the Test

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but the process usually takes just a few minutes. The blood sample is sent to a lab for analysis.

What the Results Mean

Results are typically reported as a numeric value (e.g., ng/mL or nmol/L) representing your vitamin D concentration. While reference ranges vary by lab, low levels may prompt further evaluation for deficiency, while very high levels could signal over-supplementation or other conditions.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: sputum

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

25-Hydroxy Vitamin D (Serum/Plasma)

Frequently asked questions

What causes vitamin D deficiency?
Vitamin D deficiency can result from limited sun exposure, poor diet (low intake of fatty fish, fortified foods, or supplements), certain medical conditions (e.g., malabsorption, kidney/liver disease), or medications that interfere with vitamin D metabolism.
How long does it take to get results?
Results are usually available within 1–3 business days, depending on your lab’s processing time. Your provider will discuss findings with you during your follow-up visit.
Can I take vitamin D supplements without checking my levels first?
It’s best to avoid high-dose supplements without first confirming your vitamin D status. Excessive intake can lead to toxicity, so your provider may recommend a safe dose based on 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