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Serum or plasma concentration of vitamin B12 (cobalamin)

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

This test measures your body’s level of vitamin B12, a crucial nutrient needed for red blood cell production, nerve function, and DNA synthesis. Low levels may indicate deficiencies or conditions affecting absorption.

Quick summary

["Vitamin B12 helps prevent serious health issues like anemia or nerve damage."]

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

Key facts at a glance

LOINC
111458-6
Short code
RUBV Ab Msmt Ser
Synonyms
RUBV Ab Msmt Ser
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 if you have symptoms like fatigue, weakness, numbness, or tingling in your hands and feet. It can also help diagnose conditions such as pernicious anemia, malabsorption disorders, or vitamin B12 deficiency.

What to Expect During the Test

A blood sample is taken from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause discomfort. The test is quick and typically done in a doctor’s office or lab.

Factors That Can Affect Results

Certain medications, such as certain antacids or proton pump inhibitors, can interfere with vitamin B12 absorption. Recent blood transfusions or certain medical conditions may also impact results.

Common Conditions Linked to Low Vitamin B12

Low vitamin B12 levels can be linked to conditions like pernicious anemia, celiac disease, Crohn’s disease, or long-term vegan diets. High levels may be seen in certain genetic disorders or overabsorption syndromes.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 Level

Frequently asked questions

What does a low vitamin B12 level mean?
A low vitamin B12 level may indicate a deficiency, which can lead to anemia, nerve damage, or cognitive issues. Your doctor will discuss treatment options, such as supplements or injections, based on the cause.
What does a high vitamin B12 level mean?
High vitamin B12 levels can sometimes occur in people with certain genetic disorders or conditions affecting how the body processes vitamin B12. Further testing may be needed to determine the cause.
How often should I get this test?
Your doctor will determine how often you need this test based on your health history, symptoms, and other test results. Regular monitoring may be recommended if you have a known risk for deficiency.
  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