Skip to content

Vitamin B12 (Serum or Plasma Concentration)

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

This test measures the amount of vitamin B12 (also called cobalamin) in your blood. Vitamin B12 is essential for nerve function, red blood cell production, and DNA synthesis.

Quick summary

["Vitamin B12 helps prevent serious health issues like anemia and nerve damage."]

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

Key facts at a glance

LOINC
110207-8
Short code
RABV IgG Msmt Ser
Synonyms
RABV IgG Msmt Ser
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
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 Might Be Ordered

Your doctor may recommend this test if you have symptoms like fatigue, weakness, numbness, or tingling in your hands and feet. It could also be done if you have a history of poor diet, certain medical conditions (like pernicious anemia or stomach surgery), or if you’re taking medications that interfere with B12 absorption.

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 this depends on your doctor’s instructions. Bring your medical records or a list of medications to your appointment.

What the Test Results Mean

Low levels of vitamin B12 may indicate deficiencies caused by dietary lack, malabsorption issues, or certain medical conditions. High levels are less common but could be due to certain medications or genetic factors. Your doctor will discuss results in relation to your symptoms and medical history.

Common Conditions Affecting Results

Conditions like pernicious anemia, celiac disease, Crohn’s disease, or long-term use of certain medications (like proton pump inhibitors) can lower B12 levels. Rarely, genetic disorders or liver disease may also impact results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

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), impaired absorption (e.g., due to stomach or intestinal disorders), or increased demand (e.g., during pregnancy). Chronic conditions like diabetes or kidney disease may also play a role.
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 contact you with the final report once reviewed.
Can I take supplements to raise my B12 levels?
Yes, oral or injectable B12 supplements can help raise levels, but they may not be effective if absorption is already impaired. Your doctor may recommend a different treatment, such as B12 injections or dietary changes, based on your specific needs.
  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