Skip to content

Vitamin B12 (Serum or Plasma Concentration)

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

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

Quick summary

["Check your vitamin B12 levels to ensure proper nutrient intake and avoid potential deficiencies."]

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

Key facts at a glance

LOINC
2440-6
Short code
Vit B12b SerPl-mCnc
Synonyms
Vit B12b SerPl-mCnc
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 This Test Matters

Vitamin B12 is crucial for maintaining healthy nerve cells and preventing anemia. Low levels can cause fatigue, numbness, or balance issues. This test helps identify deficiencies early, which can be treated with diet or supplements.

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 instructed by your provider. Bring your lab results and any medications you’re taking.

How the Test Works

A blood sample is taken from a vein in your arm. The lab then measures the concentration of vitamin B12 using a sensitive immunoassay or similar method to detect its presence.

What the Results Mean

Results are compared to standard reference ranges, but exact values may vary by lab. Low levels may indicate a deficiency, while high levels could signal conditions like kidney disease or certain cancers.

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 deficiency is common and can lead to serious complications if untreated, such as nerve damage, megaloblastic anemia, or cognitive decline. Early detection allows for timely intervention, often through dietary adjustments, B12 supplements, or injections.

Short name

Vitamin B12 Level

Frequently asked questions

What causes low vitamin B12 levels?
Low vitamin B12 levels can result from poor diet (e.g., vegan/vegetarian diets), malabsorption issues (e.g., pernicious anemia, celiac disease), or conditions affecting the stomach or intestines. Rarely, it may be due to medications or genetic disorders.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your healthcare provider will discuss the findings with you during your follow-up visit.
Can I take vitamin B12 supplements without checking my levels first?
While supplements can help, they shouldn’t replace a confirmed diagnosis. Always consult your doctor before starting supplements, especially if you have symptoms like fatigue or numbness, to avoid masking underlying conditions.
  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