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Vitamin B12 (Cobalamin) with Serum or Plasma Concentration Measurement

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

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

Quick summary

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

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

Key facts at a glance

LOINC
17549-7
Short code
RUBV Ab CSF-aCnc
Synonyms
RUBV Ab CSF-aCnc
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test if you have symptoms like fatigue, numbness, tingling in the hands or feet, weakness, or memory problems. It may also be checked during pregnancy, before certain surgeries, or if you have conditions like pernicious anemia, celiac disease, or gastrointestinal disorders.

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 test if your blood is drawn early in the morning. Inform your doctor about any medications, supplements, or recent vitamin intake that could affect results.

How the Test Is Performed

A healthcare provider will draw blood from a vein in your arm using a small needle. You may feel a brief sting, but it usually doesn’t cause significant discomfort. The blood sample is then sent to a lab for analysis.

What the Results Mean

Results are compared to standard reference ranges to determine if your vitamin B12 levels are within normal limits. Low levels may require further testing or treatment, while very high levels may warrant investigation for conditions like vitamin B12 toxicity.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low vitamin B12 levels can lead to megaloblastic anemia, neurological issues (e.g., cognitive decline, balance problems), or other complications. High levels may indicate malabsorption, certain medications, or rare genetic disorders. Early diagnosis and treatment can prevent long-term damage.

Short name

Vitamin B12 Level

Frequently asked questions

What causes low vitamin B12 levels?
Low vitamin B12 levels can result from dietary deficiencies (e.g., vegan/vegetarian diets), poor absorption due to conditions like atrophic gastritis, gastric bypass surgery, or celiac disease, or certain medications (e.g., proton pump inhibitors).
What are the symptoms of vitamin B12 deficiency?
Symptoms may include fatigue, weakness, pale or jaundiced skin, numbness or tingling in the hands and feet, memory loss, mood changes, or difficulty maintaining balance. Some people may not show symptoms until the deficiency is severe.
How is vitamin B12 deficiency treated?
Treatment typically involves vitamin B12 supplements (oral, injections, or nasal sprays) to restore normal levels. Lifestyle changes, such as a balanced diet rich in B12 (e.g., meat, dairy, eggs, or fortified foods), may also be recommended if dietary deficiencies are 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