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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

["Check your vitamin B12 levels if you have symptoms of deficiency or need monitoring for nutritional status."]

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

Key facts at a glance

LOINC
31131-6
Short code
MuV V Ab Titr Ser
Synonyms
MuV V Ab Titr 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 to diagnose conditions like pernicious anemia, vitamin B12 deficiency, or malabsorption disorders. It can also help evaluate symptoms such as fatigue, numbness, or neurological issues that may be linked to low vitamin B12 levels.

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 itself is quick and painless.

Common Reasons for Testing

Common reasons include unexplained fatigue, weakness, or neurological symptoms (like tingling or balance issues). It may also be part of routine blood work for patients with chronic illnesses or those on certain medications.

What the Results Mean

Results can help determine if you have a deficiency, which may require dietary changes, supplements, or medical treatment. Low levels may indicate conditions needing further investigation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 Level

Frequently asked questions

What symptoms might I experience if my vitamin B12 level is low?
Symptoms of low vitamin B12 levels can include fatigue, weakness, numbness or tingling in hands and feet, balance problems, memory issues, or mood changes. Some people may not have symptoms at first, especially if the deficiency is mild.
How often should I get this test?
Your doctor will determine how often you need testing based on your health history, symptoms, and other factors. Regular monitoring may be recommended if you have conditions like pernicious anemia, chronic kidney disease, or certain dietary restrictions.
Can I eat or drink anything before this test?
You can eat and drink normally before the test unless your doctor specifies otherwise. Avoiding alcohol or certain medications (like some antibiotics) may be advised, so check with your healthcare provider.
  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