Skip to content

25-Hydroxy Vitamin D, Serum (Total)

Published: August 9, 2026Updated: August 17, 2026

This blood test measures the total amount of vitamin D in your body, which is important for bone health and immune function.

Quick summary

["Vitamin D helps your body absorb calcium and supports immune health; low levels may indicate deficiency."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
33958-0
Short code
Vitamin D3 SerPl-sCnc
Synonyms
Vitamin D3 SerPl-sCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
30
Ref high
100
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 illnesses. It may also be used to monitor vitamin D levels in people who take vitamin D supplements or have conditions like osteoporosis or rickets.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the blood draw if instructed. Bring a list of medications to your appointment.

What Happens During the Test?

A healthcare professional will insert a small needle into a vein in your arm to draw blood. The process takes a few minutes, and you may feel a brief pinch. The blood is then sent to a lab for analysis.

What Are the Results?

Results are reported in nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L). Your provider will interpret the results in relation to your health and symptoms.

Reference range

NCBI: Vitamin D 30-100 ng/mL (sufficient)N/A

Specimen: serum

Fasting for 8-12 hours preferred for some tests. Inform about supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low vitamin D levels may increase the risk of bone disorders, infections, or certain chronic diseases. High levels can sometimes indicate over-supplementation or liver/kidney issues. Always discuss results with your provider for personalized guidance.

Short name

Vitamin D Level

Frequently asked questions

How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time.
Can I eat or drink before this test?
Most labs recommend fasting for 8–12 hours before the test, but follow your provider’s specific instructions.
What does a low vitamin D level mean?
A low level may suggest deficiency, which can affect bone health, immunity, or muscle function. Your provider will assess your symptoms and overall health to determine next steps.
  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 17, 2026. · Read our editorial policy