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Vitamin B12 (Serum or Plasma Concentration)

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

This test measures the amount 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

["Low levels may indicate deficiencies or health conditions needing attention."]

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

Key facts at a glance

LOINC
63462-6
Short code
RUBV IgG Ser Ql LA
Synonyms
RUBV IgG Ser Ql LA
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
la
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 healthcare provider may recommend this test if you have symptoms like fatigue, numbness, tingling in hands/feet, memory issues, or unexplained anemia. It’s also used to monitor vitamin B12 status in patients with certain medical conditions, such as pernicious anemia, gastric bypass surgery, or long-term vegan diets.

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 requires it. Bring any medications or supplements you take daily, as they can affect results.

How the Test Works

A blood sample is taken from a vein in your arm. The lab then measures the concentration of vitamin B12 using an immunoassay method, which detects the presence of the vitamin in your serum or plasma.

Possible Results and Next Steps

Results may be below, within, or above the normal range. Low levels often prompt further testing (like folate or intrinsic factor antibodies) or treatment with vitamin B12 supplements or injections.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin B12 deficiency can lead to serious complications, including nerve damage, anemia, and cognitive decline. Early detection through blood tests helps prevent long-term damage and guides treatment to restore normal levels.

Short name

Vitamin B12 Level

Frequently asked questions

What causes low vitamin B12 levels?
Low vitamin B12 can result from dietary deficiency (e.g., strict vegan diets), malabsorption issues (e.g., pernicious anemia, Crohn’s disease), or conditions affecting the stomach or intestines. Rarely, medications or certain medical treatments may interfere with absorption.
What symptoms might indicate a vitamin B12 deficiency?
Common symptoms include fatigue, weakness, pale or jaundiced skin, numbness or tingling in hands/feet, balance problems, memory loss, or depression. However, symptoms can be subtle and may develop slowly over time.
How is vitamin B12 deficiency treated?
Treatment typically involves vitamin B12 supplements (oral, injections, or nasal sprays) to restore levels. Lifestyle changes (e.g., fortified foods, B12-fortified nutritional supplements) may also be recommended depending on the cause.
  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