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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 serious health issues like anemia and nerve damage."]

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

Key facts at a glance

LOINC
5332-2
Short code
RUBV Ab Ser Ql LA
Synonyms
RUBV Ab 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
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 a vitamin B12 test to check for deficiencies, which can cause fatigue, weakness, numbness, or balance problems. It may also be used to diagnose conditions like pernicious anemia, malabsorption disorders, or certain types of cancer.

What to Expect Before the Test

No special preparation is usually needed. If you’re having a blood draw, tell your healthcare provider about any medications you’re taking, as some can affect results.

What Happens During the Test?

A small needle will be inserted into your arm to draw blood. The process is quick and typically causes only mild discomfort. The blood sample is then sent to a lab for analysis.

What Are Possible Results?

Results can vary based on your health and lab methods. Low levels may indicate a deficiency, while high levels could suggest certain medical conditions or lab errors.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Vitamin B12 Deficiency Can Cause Serious Health Issues

Short name

Vitamin B12 Level

Frequently asked questions

What Are the Normal Results?
Normal results depend on the lab and method used. A deficiency is often confirmed with additional tests, such as methylmalonic acid or homocysteine levels.
Can Vitamin B12 Test Results Be Affected by Medications?
Yes, certain medications—like certain antibiotics, proton pump inhibitors, or antacids—can interfere with vitamin B12 absorption or lab results. Always inform your doctor about all medications.
How Often Should I Get This Test?
Your doctor will determine the frequency based on your symptoms, medical history, and other tests. Regular monitoring may be needed if you have conditions like celiac disease or chronic kidney disease.
  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