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Serum or plasma concentration of vitamin B12 (cobalamin)

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

This test measures the amount of vitamin B12, an essential nutrient your body needs to make healthy blood and nerves. 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
56599-4
Short code
EBV VCA IgM CSF IA-aCnc
Synonyms
EBV VCA IgM CSF IA-aCnc
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
CPT
82784
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test if you have symptoms like fatigue, weakness, numbness, or tingling in your hands and feet. It’s also used to check for pernicious anemia, vitamin B12 deficiency, or conditions affecting absorption (e.g., atrophic gastritis, gastric bypass surgery).

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before drawing blood. Wear a loose shirt for easy access. If you’re pregnant, have recent surgery, or take certain medications, let your provider know.

What Happens During the Test?

A healthcare professional will insert a needle into your arm to draw blood. You may feel a slight pinch, but it usually doesn’t cause pain. The blood is sent to a lab for analysis.

What Are Possible Results?

Results are compared to standard reference ranges, but your provider will interpret them based on your health history and symptoms. Very low levels may require further testing or treatment.

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 dietary deficiency (e.g., vegetarian/vegan diets), poor absorption (e.g., due to stomach issues, surgery, or medications like proton pump inhibitors), or conditions like pernicious anemia.
How is vitamin B12 deficiency treated?
Treatment often includes vitamin B12 injections, oral supplements, or dietary changes. Your provider may monitor your levels and symptoms closely to adjust treatment.
Can vitamin B12 levels be affected by medications?
Yes, certain medications (e.g., metformin, proton pump inhibitors) or treatments (e.g., chemotherapy) can interfere with vitamin B12 absorption or metabolism. Always inform your provider about all medications you take.
  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