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Vitamin B12 (Serum) – Quantitative Measurement via Immunoassay Probe

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

This test measures the amount of vitamin B12 in your blood, an essential nutrient for nerve function and red blood cell production.

Quick summary

["Assess your vitamin B12 status to prevent deficiencies linked to nerve damage or anemia."]

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

Key facts at a glance

LOINC
106213-2
Short code
RSV A RNA BAL Ql NAA+probe
Synonyms
RSV A RNA BAL Ql NAA+probe
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-amp-tar
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 This Test Matters

Vitamin B12, also called cobalamin, is crucial for maintaining healthy nerve cells and preventing blood cell abnormalities. Low levels can lead to fatigue, numbness, or balance issues. This test helps detect deficiencies early.

How the Test Works

A small blood sample is taken from your arm. The lab uses an immunoassay probe to measure vitamin B12 concentration in your serum.

What to Expect Before the Test

No special preparation is needed, but inform your doctor about medications (e.g., certain antacids or proton pump inhibitors) that might affect results.

Common Causes of Low or High Results

Low levels may result from poor diet, pernicious anemia, or malabsorption issues. High levels are less common but can occur with certain genetic conditions or excess intake.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 Level

Frequently asked questions

How often should I get this test?
Your doctor will determine frequency based on your health history, symptoms, and risk factors. Typically, follow-up tests are scheduled if initial results are low or abnormal.
What symptoms might indicate a vitamin B12 deficiency?
Symptoms can include fatigue, weakness, tingling in hands/feet, memory problems, or unexplained weight loss. However, many people have no symptoms until deficiency is severe.
Does diet alone affect vitamin B12 test results?
Yes, a diet lacking fortified foods or animal products may lead to lower vitamin B12 levels. Your doctor may recommend dietary changes or supplements if deficiency is confirmed.
  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