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Substance concentration of vitamin B12 in serum/plasma

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

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

Quick summary

["Vitamin B12 levels help check for deficiencies that could cause fatigue, numbness, or other symptoms."]

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

Key facts at a glance

LOINC
23326-2
Short code
OvHV2 Ab Ser Ql ImStn
Synonyms
OvHV2 Ab Ser Ql ImStn
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immune-stain
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 This Test Is Done

Your doctor may order this test if you have symptoms like weakness, numbness, or unusual tiredness. It can also be used to diagnose or monitor conditions such as pernicious anemia, malabsorption issues, or certain types of malnutrition.

What to Expect Before the Test

No special preparation is needed for this blood test. You may be asked to fast for 8–12 hours before the draw, but always follow your doctor’s instructions.

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 slight pinch, but it usually doesn’t cause much discomfort.

What the Results Mean

Low levels of vitamin B12 can indicate deficiencies, while higher levels may suggest certain medical conditions or medications affecting absorption. Your doctor will interpret results in relation to your overall health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 (Serum/Plasma)

Frequently asked questions

How long does it take to get my vitamin B12 test results?
Results are typically available within 1–3 business days, depending on your lab. Follow up with your doctor to discuss findings.
Can I eat or drink before this test?
Check with your doctor or lab for fasting instructions, but generally, avoid food/drinks 8–12 hours before the draw unless advised otherwise.
What are common causes of low vitamin B12 levels?
Common causes include poor diet, pernicious anemia, celiac disease, or conditions affecting absorption in the gut. Lifestyle factors like alcohol use or certain medications may also contribute.
  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