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Vitamin B12 (Cobalamin) with Serum or Plasma Concentration

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

This test measures the amount of vitamin B12, an essential nutrient needed for healthy red blood cells, nerve function, and DNA synthesis.

Quick summary

["Low levels may indicate deficiencies linked to fatigue, nerve damage, or anemia."]

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

Key facts at a glance

LOINC
43506-5
Short code
MR Ovary-Bl
Synonyms
MR Ovary-Bl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
mr
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 weakness, numbness, memory problems, or unusual fatigue. It’s also used to diagnose conditions like pernicious anemia, vitamin B12 deficiency, or malabsorption disorders.

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 any medications you’re taking, as some (like certain blood thinners) may affect results.

How the Test Is Performed

A blood sample is taken from a vein in your arm. The sample is sent to a lab for analysis to measure vitamin B12 levels in your serum or plasma.

What the Results Mean

Results are compared to standard reference ranges, though exact values can vary by lab. Low levels may trigger further testing (e.g., methylmalonic acid or intrinsic factor antibodies) to identify underlying causes.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Chronic low levels can lead to irreversible nerve damage or megaloblastic anemia, especially if untreated. Early detection helps prevent complications like cognitive decline or muscle weakness. High levels may indicate overconsumption or certain genetic disorders.

Short name

Vitamin B12 Level

Frequently asked questions

What causes vitamin B12 deficiency?
Deficiency often stems from poor diet (e.g., vegan/vegetarian diets), malabsorption (e.g., celiac disease, atrophic gastritis), or conditions like pernicious anemia that impair vitamin B12 absorption.
Can I prevent vitamin B12 deficiency?
Yes! Eat fortified foods (e.g., nutritional yeast, plant-based milks), consider vitamin B12 supplements (if advised), or take prescribed injections. Regular monitoring may be needed if you have risk factors.
Does diet affect test results?
Yes—avoid high-dose supplements or fortified foods 24 hours before testing to prevent misleadingly high results. If you’re on long-term supplements, discuss timing with your provider.
  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