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Serum or plasma concentration of vitamin B12 (cobalamin)

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

This test measures the amount of vitamin B12 in your blood, an important nutrient needed for red blood cell production and nerve function.

Quick summary

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

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

Key facts at a glance

LOINC
20491-7
Short code
EBV VCA IgM Titr Ser
Synonyms
EBV VCA IgM Titr Ser
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
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 a vitamin B12 test if you have symptoms like fatigue, weakness, numbness, or tingling in your hands and feet. It may also be checked during pregnancy, before certain surgeries, or if you have conditions like pernicious anemia, celiac disease, or gastrointestinal disorders.

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 draw if your lab uses a specific protocol. Bring your medical records if you have conditions like diabetes or kidney disease.

How the Test Works

A small blood sample is taken from a vein in your arm. The blood is sent to a lab, where it is analyzed to measure vitamin B12 levels using an immunoassay method.

What the Results Mean

Results are reported as a concentration value (e.g., picograms per milliliter). Low levels may indicate vitamin B12 deficiency, while high levels may suggest certain liver or kidney conditions or medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low vitamin B12 levels can lead to anemia, nerve damage, or cognitive issues. High levels may require further evaluation to rule out conditions like liver disease or certain medications. Always discuss results with your doctor for personalized interpretation.

Short name

Vitamin B12 Level

Frequently asked questions

What causes low vitamin B12 levels?
Low vitamin B12 levels can result from poor diet (e.g., vegan/vegetarian diets), malabsorption issues (like pernicious anemia or Crohn’s disease), or conditions affecting the stomach or intestines. Chronic kidney disease or certain medications (e.g., metformin) may also contribute.
What are common symptoms of low vitamin B12?
Symptoms may include fatigue, weakness, pale or swollen skin, numbness or tingling in hands/feet, balance problems, memory loss, or mood changes. Some people have no symptoms until deficiency is severe.
How is vitamin B12 deficiency treated?
Treatment typically involves vitamin B12 supplements (injections, oral, or nasal sprays) to restore levels. Lifestyle changes (e.g., fortified foods, B12-rich meals) may also help if diet is the cause. Follow-up tests are often needed to monitor progress.
  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