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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. Vitamin B12 is essential for nerve function, red blood cell production, and DNA synthesis.

Quick summary

["Low levels may indicate deficiencies or health concerns needing attention."]

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

Key facts at a glance

LOINC
5331-4
Short code
RUBV Ab Ser Ql HAI
Synonyms
RUBV Ab Ser Ql HAI
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
1.5
Ref high
9
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
hai
CPT
83002
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 healthcare provider may order this test to check for vitamin B12 deficiency, which can cause fatigue, numbness, or neurological issues. It may also be done if you have conditions like pernicious anemia, celiac disease, or certain 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 it involves drawing blood from a vein.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. You may feel a small pinch, but it usually takes only a few minutes.

What Are Possible Results?

Results are compared to standard ranges, but exact values can vary by lab. Low levels may trigger further testing or dietary or medical interventions.

Reference range

Follicular: 1.5-9.0 mIU/mLN/A

Specimen: serum

For females: inform if menstrual cycle status. For certain tests, timing within menstrual cycle may matter.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low vitamin B12 levels can lead to anemia, nerve damage, or cognitive issues. High levels may indicate overconsumption or certain genetic conditions. Your provider will discuss results in the context of your health history.

Short name

Vitamin B12 Level

Frequently asked questions

What causes vitamin B12 deficiency?
Deficiency can result from poor diet (e.g., vegan/vegetarian diets), malabsorption issues (e.g., stomach or intestinal disorders), or conditions like pernicious anemia that impair vitamin B12 absorption.
Can vitamin B12 deficiency be treated?
Yes, treatment often involves supplements (oral or injections) or dietary changes. Follow-up tests may be needed to monitor levels and symptoms.
How often should I get this test?
Your provider will determine frequency based on your health status, symptoms, or risk factors. Regular monitoring may be recommended if you have conditions linked to B12 deficiency.
  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