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Vitamin B12 (Serum or Plasma Mass Concentration)

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

This test measures the amount of vitamin B12 in your blood. Vitamin B12 is essential for red blood cell production, nerve function, and DNA synthesis.

Quick summary

["Low levels may indicate deficiencies linked to nerve damage or anemia; high levels may signal excess intake or certain genetic conditions."]

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

Key facts at a glance

LOINC
2435-6
Short code
HVA Ser-mCnc
Synonyms
HVA Ser-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
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 doctor may order this test if you have symptoms like fatigue, numbness, tingling in the hands or feet, weakness, or digestive issues. It’s also used to check for pernicious anemia, vitamin B12 deficiency, or conditions like celiac disease or alcoholism that can interfere with absorption.

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 specific protocol. Bring your test list and ID to confirm you’re the right patient.

How the Test Works

A blood sample is taken from a vein in your arm. The lab then measures the vitamin B12 concentration using a specialized technique, often an immunoassay or chemiluminescent method.

What the Results Mean

Results are compared to standard reference ranges, though exact values can vary by lab. Low levels may prompt further testing for causes like dietary deficiency, malabsorption, or medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 Level

Frequently asked questions

What causes vitamin B12 deficiency?
Deficiency often results from poor dietary intake (e.g., vegan diets), malabsorption (e.g., atrophic gastritis, Crohn’s disease), or conditions like pernicious anemia that block B12 absorption.
Can I take supplements to prevent deficiency?
Yes, oral or injectable B12 supplements can help, but absorption may be impaired in some cases. Follow your doctor’s advice—some patients need lifelong treatment.
Does stress or diet affect B12 levels?
Chronic stress or extreme dietary changes (e.g., sudden veganism) may temporarily lower B12, but long-term deficiency requires medical evaluation to identify root causes.
  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