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Serum or plasma concentration of vitamin B12 (substance 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

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

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

Key facts at a glance

LOINC
44571-8
Short code
FLUBV Ag Nph Ql IF
Synonyms
FLUBV Ag Nph Ql IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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, weakness, or neurological symptoms. It may also be used to monitor conditions like pernicious anemia, malabsorption disorders, or certain types of cancer.

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 your blood is drawn early in the morning. Bring any medications you’re currently taking.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but it typically only takes a few minutes. The blood sample is then sent to a lab for analysis.

What Are Possible Results?

Results are compared to standard reference ranges, but your specific values will be reviewed by your doctor. Low levels may signal deficiency, while very high levels could indicate conditions like kidney disease or certain medications.

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 require further investigation to rule out conditions like kidney disease or excessive vitamin B12 supplements. Your doctor will interpret results in the context of your symptoms and medical history.

Short name

Vitamin B12 Level

Frequently asked questions

What causes low vitamin B12 levels?
Low vitamin B12 levels can result from dietary deficiencies (e.g., vegan/vegetarian diets), malabsorption issues (e.g., pernicious anemia, Crohn’s disease), or conditions affecting absorption in the stomach or intestines.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will discuss them with you during your follow-up visit.
Can I take vitamin B12 supplements if my levels are low?
Only your doctor can recommend supplements or treatments. They may suggest oral supplements, injections, or dietary changes based on your specific needs and underlying conditions.
  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