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Vitamin B12 (Serum or Plasma Concentration)

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of vitamin B12, a vital nutrient needed for red blood cell production and nerve function, in your blood.

Quick summary

["Vitamin B12 helps prevent nerve damage and anemia; low levels may indicate deficiencies or underlying health concerns."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
55882-5
Short code
Vit B12b Fld-sCnc
Synonyms
Vit B12b Fld-sCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
200
Ref high
900
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 healthcare provider may order this test if you have symptoms like fatigue, weakness, numbness, or tingling in your hands and feet. It can also be part of screening for pernicious anemia, certain gastrointestinal conditions, or malabsorption issues.

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 different method. Bring any medications you’re taking to discuss with your provider.

What Happens During the Test?

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

What Do Results Mean?

Results help determine if your vitamin B12 levels are within normal ranges. Low levels may require further testing or treatment, such as vitamin supplements or injections.

Reference range

NCBI: Vitamin B12 200-900 pg/mLN/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin B12 plays a critical role in maintaining nerve function and red blood cell production. Low levels can lead to anemia, nerve damage, or other neurological issues, while high levels may indicate conditions like vitamin B12 overload (rare) or certain metabolic disorders.

Short name

Vitamin B12 Level

Frequently asked questions

What causes low vitamin B12 levels?
Low vitamin B12 can result from poor diet (lack of meat, fish, or fortified foods), conditions affecting absorption (like pernicious anemia or celiac disease), or certain medications (e.g., proton pump inhibitors).
How is vitamin B12 deficiency treated?
Treatment often involves oral supplements, injections, or increasing vitamin B12-rich foods. Your provider may monitor your levels and symptoms to adjust treatment.
Can vitamin B12 levels be affected by other health conditions?
Yes, conditions like kidney disease, certain cancers, or long-term alcohol use may influence vitamin B12 levels. Always discuss your full medical history with your provider.
  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 17, 2026. · Read our editorial policy