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Vitamin B12 (Serum Concentration)

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

This test measures the level of vitamin B12 (also called cobalamin) in your blood. Vitamin B12 is essential for nerve function, red blood cell production, and DNA synthesis.

Quick summary

["Vitamin B12 helps prevent serious health issues like anemia and nerve damage."]

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

Key facts at a glance

LOINC
95650-8
Short code
MAYV NAb Titr Spec Nt
Synonyms
MAYV NAb Titr Spec Nt
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
neut
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 Might Be Ordered

Your doctor may recommend this test if you have symptoms such as fatigue, weakness, numbness, or tingling in your hands and feet. It could also be ordered if you have a history of poor diet, certain medical conditions (like pernicious anemia or celiac disease), or if you’re taking medications that interfere with vitamin B12 absorption.

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 test if it involves drawing blood from a vein. If you’re taking certain medications, let your doctor know beforehand.

How the Test Is Performed

A healthcare professional will draw blood from a vein in your arm using a small needle. The blood sample will be sent to a lab for analysis using an immunoassay method to measure vitamin B12 levels.

What the Results Mean

Low vitamin B12 levels may indicate deficiencies caused by dietary lack, malabsorption issues, or certain medical conditions. High levels are less common but may occur in some genetic disorders or with certain medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin B12 deficiency can lead to serious health problems, including anemia (reduced red blood cells), nerve damage, and cognitive issues. Early detection and treatment (such as supplements or injections) can prevent these complications.

Short name

Vitamin B12

Frequently asked questions

What causes low vitamin B12 levels?
Low vitamin B12 levels can result from poor diet (e.g., vegan/vegetarian diets without fortified foods), conditions that interfere with absorption (like pernicious anemia or Crohn’s disease), or certain medications that reduce absorption.
How long does it take to get results?
Test results typically arrive within 1–3 business days, depending on your lab’s processing time. Your doctor will discuss the findings with you during your follow-up visit.
Can vitamin B12 levels be affected by medications?
Yes, some medications—like proton pump inhibitors (for acid reflux), metformin (for diabetes), or certain antibiotics—may lower vitamin B12 levels by affecting its absorption in the gut.
  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