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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, an essential nutrient needed for red blood cell production and nerve function, in your blood.

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
5157-3
Short code
EBV VCA IgG Ser IA-aCnc
Synonyms
EBV VCA IgG Ser IA-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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 Is This Test Done?

Your healthcare provider may order this test if you have symptoms like fatigue, numbness, tingling in the hands or feet, or unexplained anemia. It’s also used to screen for pernicious anemia, vitamin B12 deficiency, or conditions affecting absorption (e.g., gastric bypass surgery).

What to Expect Before the Test

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

What Happens During the Test?

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

What Are Possible Results?

Results are typically reported as a concentration in picograms per milliliter (pg/mL) or picomoles per liter (pmol/L). Low levels may indicate deficiency, while high levels could suggest conditions like kidney disease or certain 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 low vitamin B12 levels?
Low vitamin B12 levels can result from poor diet (e.g., vegan/vegetarian diets), malabsorption issues (e.g., atrophic gastritis, celiac disease), or conditions like pernicious anemia. Certain medications (e.g., metformin) may also contribute.
What are the symptoms of vitamin B12 deficiency?
Symptoms may include fatigue, weakness, pale or jaundiced skin, numbness or tingling in the hands/feet, dizziness, memory problems, or mood changes. Deficiency can develop slowly, so symptoms may not appear until severe.
How is vitamin B12 deficiency treated?
Treatment typically involves oral or injectable vitamin B12 supplements. If absorption is the issue, your provider may recommend dietary changes or additional treatments like gastric acid supplements. Follow-up tests may be needed to monitor levels.
  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