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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 needed for healthy red blood cells, nerve function, and DNA synthesis.

Quick summary

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

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

Key facts at a glance

LOINC
17016-7
Short code
FLUBV IgM Ser-aCnc
Synonyms
FLUBV IgM Ser-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 This Test Might Be Ordered

Your doctor may recommend this test if you have symptoms like weakness, numbness, tingling in the hands or feet, unusual fatigue, or unexplained anemia. It may also be checked during pregnancy, before certain surgeries, or if you have conditions like pernicious anemia, celiac disease, or gastrointestinal disorders that affect nutrient absorption.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the draw if your lab uses a specific method. Bring your test results and any medications you’re taking to your appointment.

How the Test Works

A blood sample is taken from a vein in your arm. The lab analyzes the serum or plasma for vitamin B12 levels using an immunoassay or similar method to detect its presence.

What the Results Mean

Results are compared to a reference range, but exact values can vary by lab. Low levels may indicate deficiency, while high levels may suggest overconsumption or certain medical conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low vitamin B12 levels can lead to megaloblastic anemia, neurological issues, or cognitive problems. High levels may be harmless but could signal conditions like vitamin B12 toxicity (rare) or overuse of supplements. Regular monitoring is advised for patients with chronic conditions affecting absorption.

Short name

Vitamin B12 Level

Frequently asked questions

Could I get this test at home?
No, vitamin B12 testing requires a blood draw in a clinical setting. Over-the-counter tests for vitamin B12 are not FDA-approved for clinical use.
What causes vitamin B12 deficiency?
Deficiency often results from poor diet (vegan/vegetarian diets), malabsorption (e.g., from stomach surgery, celiac disease, or pernicious anemia), or conditions like Crohn’s disease.
Can I take supplements to fix a low vitamin B12 level?
Yes, oral or injectable supplements can correct deficiency. Your doctor may recommend them after confirming low levels and ruling out other causes. Follow-up testing is often needed to monitor progress.
  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