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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. Low levels may indicate deficiencies or certain health conditions.

Quick summary

["Check your vitamin B12 levels if you have symptoms like fatigue, numbness, or trouble concentrating."]

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

Key facts at a glance

LOINC
5159-9
Short code
EBV VCA IgM Ser IA-aCnc
Synonyms
EBV VCA IgM Ser IA-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
CPT
82784
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 to diagnose or monitor conditions such as pernicious anemia, vitamin B12 deficiency, or malabsorption issues (like celiac disease or Crohn’s disease). It can also be used to screen for risk factors in people with risk factors like vegan/vegetarian diets, older adults, or those with certain gastrointestinal disorders.

What to Expect Before the Test

No special preparation is needed for most vitamin B12 tests. However, if you’re taking certain medications (like certain antibiotics or proton pump inhibitors), your doctor may advise adjusting timing. Avoid heavy meals 2 hours before the blood draw if instructed.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. You may feel a slight pinch, but the process is quick. The blood sample is then sent to a lab for analysis.

What Are Possible Results?

Results are reported as a concentration (typically in picograms per milliliter or picomoles per liter). Low levels may indicate deficiency, while high levels could signal conditions like kidney disease or certain medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low vitamin B12 levels can lead to anemia (reduced red blood cells), neurological issues (like tingling, memory problems, or balance issues), or fatigue. High levels may not always be harmful but can sometimes signal underlying conditions like kidney disease or excessive intake from supplements.

Short name

Vitamin B12 Level

Frequently asked questions

What causes low vitamin B12 levels?
Low vitamin B12 levels can result from dietary deficiency (e.g., strict vegan diets), poor absorption (e.g., pernicious anemia, gastric bypass surgery), or conditions affecting the stomach or intestines.
What symptoms might I experience if my vitamin B12 is low?
Symptoms of low vitamin B12 may include fatigue, weakness, pale or yellowish skin, numbness or tingling in hands/feet, dizziness, memory problems, or difficulty concentrating.
Can vitamin B12 levels be affected by medications?
Yes, certain medications like proton pump inhibitors (e.g., Prilosec), metformin (for diabetes), or antibiotics may interfere with vitamin B12 absorption or levels. Always discuss with your doctor if you’re on these medications.
  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