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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, an essential nutrient for nerve function and red blood cell production.

Quick summary

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

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

Key facts at a glance

LOINC
22496-4
Short code
RUBV Ab Ser Ql
Synonyms
RUBV Ab Ser Ql
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, numbness, tingling in hands/feet, weakness, or unusual food cravings. It may also be checked during pregnancy, before certain surgeries, or if you have conditions like pernicious anemia, celiac disease, or chronic alcohol use.

What to Expect Before the Test

No special preparation is needed unless instructed. You may have blood drawn from a vein in your arm. If you’re on a vitamin B12 supplement, check with your doctor first—your results may be affected.

What the Results Mean

Results help determine if you have a vitamin B12 deficiency or other conditions affecting absorption. Low levels may prompt further testing or treatment, while normal results suggest adequate vitamin B12 levels.

Common Conditions Linked to Low Vitamin B12

Deficiencies can stem from poor diet (e.g., vegan/vegetarian diets), malabsorption issues (e.g., atrophic gastritis), or conditions like pernicious anemia or kidney disease. Symptoms may develop slowly and include fatigue, memory loss, or balance problems.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 Level

Frequently asked questions

Why might my vitamin B12 test be ordered even if I eat a balanced diet?
Your doctor may order it to check for hidden deficiencies, especially if you have symptoms like fatigue or nerve issues, or if you have conditions that affect vitamin absorption (e.g., stomach problems, kidney disease). Some medications or medical conditions can also interfere with vitamin B12 levels.
What happens if my vitamin B12 levels are low?
If low, your doctor may recommend supplements (oral or injections) to restore levels, especially if you have symptoms like fatigue or nerve problems. They may also suggest dietary changes or further testing to find the cause.
Can vitamin B12 levels change over time?
Yes, levels can fluctuate due to diet, health conditions, or medications. Regular monitoring may be needed if you have ongoing symptoms or risk factors (e.g., chronic illness, pregnancy, or older age). Follow your doctor’s advice for follow-up testing.
  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