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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 in your blood, which is important for nerve function, red blood cell production, and overall health.

Quick summary

["Vitamin B12 helps prevent deficiencies that can cause fatigue, neurological issues, or anemia."]

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

Key facts at a glance

LOINC
44575-9
Short code
FLUBV Ag Nose Ql IA
Synonyms
FLUBV Ag Nose Ql IA
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
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 weakness, numbness, memory problems, or unusual fatigue. It’s also used to check for pernicious anemia, vitamin B12 deficiency, or malabsorption issues (like celiac disease or atrophic gastritis). Blood tests for folate and red blood cell counts are often done alongside this one.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if your lab uses a specific protocol. Bring any medications you’re taking, as some (like certain blood thinners) may affect results.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. The process takes just a few minutes, and you may feel a slight pinch. The sample is sent to a lab for analysis.

What Do Results Mean?

Low levels may indicate vitamin B12 deficiency, while high levels could suggest liver disease, certain cancers, or other conditions. Your doctor will interpret results in the context of your symptoms and overall health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 Level

Frequently asked questions

Could I have symptoms without a low B12 level?
Yes, some people may not show symptoms until deficiency is severe. Fatigue, tingling in hands/feet, or memory issues are common early signs, but some people feel fine until levels drop significantly.
Does diet affect this test?
Yes—high intake of folate (leafy greens, fortified foods) or certain supplements can mask B12 deficiency. Avoiding excessive folate for 4–6 weeks before testing may improve accuracy if you’re at risk.
Is this test the same as a folate test?
No, these tests measure different nutrients. Folate is a B-vitamin involved in cell growth, while B12 supports nerve function and red blood cell production. Both deficiencies can cause similar symptoms but require different treatments.
  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