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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, which is important for nerve function, red blood cell production, and overall health.

Quick summary

["Vitamin B12 helps prevent nerve damage and supports red blood cell health."]

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

Key facts at a glance

LOINC
43810-1
Short code
RUBV Ab Ser Ql IA
Synonyms
RUBV Ab 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
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 to check for vitamin B12 deficiency, which can cause fatigue, numbness, weakness, or anemia. It may also be used to monitor treatment for conditions like pernicious anemia or to evaluate symptoms like unexplained weakness or neurological issues.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood, which usually takes a few minutes. If you’re on blood thinners, let your doctor know before the test.

What the Results Mean

Low levels of vitamin B12 can indicate deficiency, while high levels may suggest conditions like certain cancers or liver disease. Your doctor will interpret results in the context of your symptoms and overall health.

Common Causes of Abnormal Results

Deficiency may result from poor diet, malabsorption issues (like pernicious anemia or celiac disease), or conditions that affect vitamin B12 absorption. High levels could be due to overabsorption, certain medications, or underlying health conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Vitamin B12 Level

Frequently asked questions

What symptoms might I experience if my vitamin B12 levels are low?
Symptoms of low vitamin B12 levels may include fatigue, weakness, numbness or tingling in hands/feet, balance problems, memory issues, or a sore tongue. Early deficiency can be hard to notice, so regular monitoring is important for those at higher risk.
How often should I get this test if I have a history of vitamin B12 issues?
If you’ve had past deficiencies or conditions affecting absorption (like atrophic gastritis), your doctor may recommend testing every 1–2 years or more frequently depending on your treatment and symptoms. Follow their specific guidance.
Can diet alone fix vitamin B12 deficiency?
Dietary sources like meat, fish, eggs, and fortified foods can help, but some people (like vegetarians/vegans) may need supplements or injections. Your doctor may prescribe B12 if diet alone isn’t enough to correct 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