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Vitamin B12 (Serum or Plasma Concentration)

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

["Low levels may indicate deficiencies or underlying health concerns that need attention."]

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

Key facts at a glance

LOINC
31957-4
Short code
RUBV Ag Eye Ql
Synonyms
RUBV Ag Eye Ql
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 balance problems. It may also be recommended if you have conditions like pernicious anemia, celiac disease, or other gastrointestinal issues that can affect nutrient absorption.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for a few hours before the blood draw, but this depends on your doctor’s instructions. Bring any medications you’re currently taking.

What Happens During the Test?

A healthcare provider will insert a small needle into your arm to draw blood. The process is quick and typically causes only minor discomfort. The blood sample will be sent to a lab for analysis.

What Are Possible Results?

Results can vary based on individual health and lab methods. Low levels may suggest vitamin B12 deficiency, while normal or high levels may indicate adequate stores. Your doctor will interpret the 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 (low intake of meat, fish, or fortified foods), conditions affecting absorption (like pernicious anemia or celiac disease), or certain medications that interfere with absorption.
What are the symptoms of vitamin B12 deficiency?
Symptoms may include fatigue, weakness, numbness or tingling in hands and feet, balance issues, memory problems, or a sore, red tongue. Some people may not show symptoms until the deficiency is severe.
How is vitamin B12 deficiency treated?
Treatment often involves vitamin B12 supplements (oral, injections, or nasal sprays) to restore levels. Lifestyle changes, such as a diet rich in vitamin B12 sources, may also be recommended under medical guidance.
  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