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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 in your blood, which is essential 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
30984-9
Short code
Silver Birch (rBet v) 1 IgE Qn
Synonyms
Silver Birch (rBet v) 1 IgE Qn
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 may also be used to diagnose or monitor conditions such as pernicious anemia, malabsorption disorders, or vitamin B12 deficiency.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood. If you’re on a blood thinner, let your doctor know before the test.

What the Results Mean

Results help determine if your vitamin B12 levels are too low, normal, or too high. Low levels can affect how your body uses energy and may require treatment like vitamin B12 supplements or injections.

Common Causes of Low or High Levels

Low vitamin B12 levels can result from poor diet, certain medications, or conditions like Crohn’s disease or alcoholism. High levels are less common but may occur with certain genetic disorders or overuse of supplements.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin B12 deficiency can lead to serious health issues, including nerve damage, anemia, and cognitive problems. Early detection allows for timely treatment to prevent complications. High levels may not always indicate a problem but should be evaluated by your doctor.

Short name

Vitamin B12 Level

Frequently asked questions

What causes vitamin B12 deficiency?
Vitamin B12 deficiency can be caused by poor dietary intake (e.g., vegan/vegetarian diets), conditions that interfere with absorption (like pernicious anemia or celiac disease), or certain medications that reduce stomach acid.
How is vitamin B12 deficiency treated?
Treatment usually involves vitamin B12 supplements (oral or injections) to restore normal levels. Lifestyle changes, such as a balanced diet or avoiding certain medications, may also help prevent recurrence.
Can high vitamin B12 levels be dangerous?
Rarely, very high vitamin B12 levels can cause health issues like heart problems or diabetes, but this is uncommon. Most high levels are harmless and require no treatment unless further investigation is needed.
  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