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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 red blood cell production, nerve function, and DNA synthesis.

Quick summary

["Low levels may indicate deficiencies or health conditions needing attention."]

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

Key facts at a glance

LOINC
9535-6
Short code
FLUBV IgG Titr Ser
Synonyms
FLUBV IgG Titr Ser
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
8
Ref high
61
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82977
SNOMED
3110003
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 this test if you have symptoms like fatigue, numbness, tingling in hands/feet, weakness, or unexplained anemia. It’s also used to check for pernicious anemia, malabsorption issues, or other conditions affecting vitamin B12 absorption.

What to Expect Before the Test

No special preparation is needed, but you may fast for 8–12 hours before the draw if instructed. Bring any medications or supplements you take daily. Avoid large doses of vitamin B12 supplements unless directed by your doctor.

How the Test Is Performed

A blood sample is taken from a vein in your arm by a healthcare professional. The blood is sent to a lab for analysis using an immunoassay method to measure vitamin B12 concentration.

What the Results Mean

Results are compared to standard reference ranges for your age and health status. Low levels may trigger further testing or treatment recommendations, while normal levels suggest adequate vitamin B12 status.

Reference range

Adult males: 8-61 U/L; Adult females: 5-36 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Vitamin B12 Deficiency Can Cause Serious Health Issues

Short name

Vitamin B12 Level

Frequently asked questions

What are common symptoms of low vitamin B12 levels?
Symptoms may include fatigue, weakness, pale or yellowish skin, numbness or tingling in hands/feet, balance problems, memory loss, or mood changes. Some people have no symptoms at all.
Can vitamin B12 deficiency be treated?
Yes, treatment often involves oral supplements, injections, or nasal sprays of vitamin B12. Lifestyle changes like improving diet (e.g., lean meats, eggs, dairy) or addressing underlying conditions (e.g., stomach issues) may also help.
How often should I get this test?
Your doctor will determine frequency based on your health history, symptoms, and test results. Regular monitoring may be needed if you have conditions like celiac disease, Crohn’s disease, or long-term vegan diets.
  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