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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 need medical attention."]

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

Key facts at a glance

LOINC
111437-0
Short code
VZV Ab Msmt Ser
Synonyms
VZV 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 healthcare provider may order this test to check for vitamin B12 deficiency, which can cause fatigue, numbness, weakness, or other neurological symptoms. It may also be done if you have conditions like pernicious anemia, malabsorption issues, or certain dietary restrictions.

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 test if it involves drawing blood. Wear a comfortable shirt for easy access to your arm.

How the Test Is Performed

A healthcare professional will insert a needle into your vein (usually in your arm or hand) to draw blood. The process is quick and may cause a slight sting. The blood sample is then sent to a lab for analysis.

What the Results Mean

Results may be below, within, or above the normal range for vitamin B12. Low levels may indicate deficiencies, while high levels could suggest certain medical conditions or medications. Your doctor will interpret results in the context of your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 Level

Frequently asked questions

What causes low vitamin B12 levels?
Low vitamin B12 levels can result from poor diet (e.g., vegan/vegetarian diets without fortified foods), conditions affecting absorption (like pernicious anemia or Crohn’s disease), or certain medications. Chronic kidney disease or excessive alcohol use may also contribute.
What symptoms might I experience if my vitamin B12 is low?
Symptoms of low vitamin B12 can include fatigue, weakness, numbness or tingling in hands/feet, balance problems, memory loss, or mood changes. Some people may not notice symptoms until the deficiency is severe.
How is vitamin B12 deficiency treated?
Treatment typically involves vitamin B12 supplements (oral, injections, or nasal sprays) to restore levels. Lifestyle changes, such as eating fortified foods or adding vitamin B12 to your diet, may also help. Severe cases may require long-term monitoring.
  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