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Vitamin B12 (Serum or Plasma Concentration)

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

This test measures the level of vitamin B12, an essential nutrient needed for healthy nerve cells and red blood cells. Low levels may indicate deficiencies or underlying health conditions.

Quick summary

["Vitamin B12 helps prevent nerve damage and anemia; low levels need medical attention."]

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

Key facts at a glance

LOINC
24217-2
Short code
FLUBV Ab sp1 Titr Ser CF
Synonyms
FLUBV Ab sp1 Titr Ser CF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
comp-fix
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 the hands or feet, weakness, or memory problems. It’s also used to check for pernicious anemia, vitamin B12 deficiency, or conditions like celiac disease or gastric surgery that can affect absorption.

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 draw if your lab uses a different method. Bring any medications or supplements you take regularly to your appointment.

What Happens During the Test?

A healthcare provider will collect a blood sample from a vein in your arm. You may feel a slight pinch, but it’s usually over quickly. The blood is then sent to a lab for analysis.

What Are Possible Results?

Results are compared to a general reference range, but your doctor will interpret them in the context of your health history and symptoms. Very low levels may require further testing or treatment.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12

Frequently asked questions

What causes low vitamin B12 levels?
Low vitamin B12 can result from poor diet (e.g., vegan/vegetarian diets without fortified foods), malabsorption issues (like pernicious anemia or celiac disease), or conditions affecting the stomach or intestines (e.g., gastric bypass surgery).
How is vitamin B12 deficiency treated?
Treatment depends on the cause. Oral supplements or injections of vitamin B12 are common. If absorption is the issue, your doctor may recommend lifelong supplementation. Follow-up tests may be needed to monitor levels and symptoms.
Can vitamin B12 levels be affected by medications?
Yes, certain medications—like proton pump inhibitors (for acid reflux), metformin (for diabetes), or antacids—can interfere with vitamin B12 absorption. Always inform your doctor about all medications you take.
  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