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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. Vitamin B12 is essential for nerve function, red blood cell production, and DNA synthesis.

Quick summary

["Vitamin B12 helps prevent nerve damage and anemia; 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
24115-8
Short code
EBV VCA IgM Ser Ql IA
Synonyms
EBV VCA IgM Ser Ql IA
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, weakness, numbness, or balance issues. It may also be used to screen for pernicious anemia, vitamin B12 deficiency, or conditions affecting absorption (e.g., celiac disease, gastric bypass surgery).

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 blood draw. If you’re on certain medications (e.g., metformin), let your provider know.

How the Test Works

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

Possible Results and Next Steps

Low levels may indicate deficiency (often due to poor diet, malabsorption, or medications). High levels could signal liver disease or other conditions. Your provider will discuss results and recommend follow-up if needed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 Level

Frequently asked questions

What Are Normal Results?
Normal results vary by lab, but typical ranges are between 200–900 picograms per milliliter (pg/mL). If your result is outside this range, further testing (e.g., methylmalonic acid or homocysteine) may be needed.
How Often Should I Get This Test?
If you have a known deficiency, your provider may recommend periodic monitoring. Otherwise, this test is often done as part of a routine checkup or when symptoms suggest a deficiency.
Can Diet or Supplements Affect This Test?
Yes—high intake of vitamin B12 supplements or fortified foods can raise results. Avoid taking large doses unless directed by your provider.
  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