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Plasma or serum vitamin B12 concentration (mass concentration)

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

This test measures the level of vitamin B12, a crucial nutrient that helps your body make healthy red blood cells and nerve cells. Low levels may indicate deficiencies or certain health conditions.

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
28542-9
Short code
PMV Bld
Synonyms
PMV Bld
Category
hematology
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your doctor may order a vitamin B12 test to check for deficiencies, especially if you have symptoms like fatigue, numbness, weakness, or unusual food cravings. It can also help diagnose conditions like pernicious anemia, certain gastrointestinal disorders, or malabsorption issues.

What to Expect Before the Test

No special preparation is needed unless instructed by your doctor. You may have a simple blood draw from a vein in your arm. If testing urine or saliva, follow any specific instructions provided.

What the Results Mean

Results are interpreted by your healthcare provider based on your symptoms, medical history, and other test results. Very low levels may require supplements or further evaluation for underlying causes.

Common Causes of Low or High Levels

Low vitamin B12 levels can result from poor diet, certain medications, or conditions affecting absorption (e.g., celiac disease, atrophic gastritis). High levels are less common but may occur with certain genetic disorders or prolonged use of supplements.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin B12 deficiency can lead to serious health issues, including nerve damage, anemia, and cognitive problems. Early detection and treatment (such as supplements or injections) can prevent complications. Your doctor will discuss results and next steps with you.

Short name

Vitamin B12 (B12) blood test

Frequently asked questions

What symptoms might indicate a vitamin B12 deficiency?
Symptoms may include fatigue, weakness, numbness or tingling in hands/feet, balance problems, memory loss, or a smooth, red tongue. If you experience these, mention them to your doctor.
How is vitamin B12 tested in the blood?
The test measures the amount of vitamin B12 in your blood, usually taken from a vein. If results are unclear, your doctor may order additional tests, such as a methylmalonic acid (MMA) or homocysteine test.
Can vitamin B12 levels change over time?
Yes, levels can fluctuate due to diet, medications, or health conditions. Regular monitoring may be needed if you have ongoing symptoms or risk factors for deficiency.
  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