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Serum or Plasma Vitamin B12 (Cobalamin) Concentration

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

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

Quick summary

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

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

Key facts at a glance

LOINC
22497-2
Short code
RUBV Ab Titr Ser
Synonyms
RUBV Ab Titr Ser
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
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 doctor 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, celiac disease).

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 method. Bring your recent test results if you have them.

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 may vary by lab. Low levels may signal deficiency, while high levels could indicate liver disease or certain medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin B12 deficiency can lead to anemia, nerve damage, or cognitive issues. Early detection helps prevent complications like weakness, balance problems, or memory loss. Your doctor may recommend supplements, dietary changes, or further testing if levels are low.

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, Crohn’s disease), or conditions affecting stomach acid production.
What symptoms might I experience if my vitamin B12 is low?
Symptoms may include fatigue, pale skin, numbness/tingling in extremities, memory problems, or difficulty concentrating. Some people have no symptoms until deficiency is severe.
How is vitamin B12 deficiency treated?
Treatment often involves B12 supplements (oral, injections, or nasal sprays) to restore levels. Lifestyle changes (e.g., fortified foods) may also help if diet is the cause.
  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