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Vitamin B12 (Serum) with Quantitative Measurement

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

This test measures the level of vitamin B12, a crucial nutrient that helps your body make healthy red blood cells and nerve cells.

Quick summary

["Vitamin B12 helps prevent anemia and nerve damage; low levels may indicate deficiencies or underlying health conditions."]

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

Key facts at a glance

LOINC
40542-3
Short code
RUBV Ab Titr CSF LA
Synonyms
RUBV Ab Titr CSF LA
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
la
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test if you have symptoms like fatigue, numbness, tingling in hands/feet, or trouble with balance. It’s also used to check for vitamin B12 deficiency, especially in people with conditions like pernicious anemia, celiac disease, or those on long-term vitamin B12-folate supplements.

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 blood is collected in the morning. Bring any medications or supplements you’re taking to discuss with your provider.

What Happens During the Test?

A healthcare professional will insert a needle into a vein in your arm to draw a small amount of blood. The process usually takes a few minutes and may cause a brief sting. The blood sample is then sent to a lab for analysis.

What Are Possible Results?

Results are typically reported as a concentration of vitamin B12 in the blood. Low levels may indicate deficiency, while high levels could suggest conditions like kidney disease or certain medications. Your provider will interpret results in the context of your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low vitamin B12 levels can lead to megaloblastic anemia (large, immature red blood cells), nerve damage (neuropathy), and cognitive issues. Deficiencies are often linked to poor diet, malabsorption (e.g., from stomach/gut disorders), or excessive alcohol use. High levels may signal kidney dysfunction or certain medications (e.g., metformin). Early diagnosis helps prevent long-term complications.

Short name

Vitamin B12 (Serum)

Frequently asked questions

What causes vitamin B12 deficiency?
Vitamin B12 deficiency can result from poor dietary intake (e.g., vegan/vegetarian diets without fortified foods), conditions that impair absorption (like pernicious anemia or atrophic gastritis), or long-term use of certain medications (e.g., proton pump inhibitors). Chronic kidney disease or excessive alcohol use may also contribute.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your healthcare provider will contact you once they have the results and discuss next steps.
Can I take supplements before the test?
If your provider has prescribed vitamin B12 supplements, follow their instructions carefully. Avoid large doses of over-the-counter supplements unless advised, as they may affect test accuracy. Always check with your provider before taking any supplements.
  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