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Vitamin B12 (Cobalamin) with Serum or Plasma Substance Concentration Measurement

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of vitamin B12, a crucial nutrient needed for red blood cell production and nerve function, in your blood.

Quick summary

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

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
75096-8
Short code
VLCFA C26:0 EntSub RBC
Synonyms
VLCFA C26:0 EntSub RBC
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
4.2
Ref high
5.9
Critical range
2 N/A – 7 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85041
SNOMED
900000000000003001
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test to check for vitamin B12 deficiency, which can cause fatigue, weakness, or nerve problems. It may also be done if you have symptoms like numbness, tingling, or unusual food cravings, or if you have conditions like pernicious anemia or gastrointestinal disorders that affect nutrient absorption.

What to Expect Before the Test

No special preparation is usually needed, but your doctor might advise avoiding certain supplements (like folic acid) or foods (like liver) for a few days before testing if instructed. Bring any recent medications to your appointment.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. The sample is sent to a lab for analysis, where vitamin B12 levels are measured using a specialized immunoassay or similar method.

What Are the Results?

Results are compared to standard ranges, but exact values may vary by lab. Low levels may indicate deficiency, while high levels could signal conditions like kidney disease or certain cancers. Follow-up testing or treatment may be recommended based on your results.

Reference range

Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A

Specimen: whole-blood

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin B12 deficiency can lead to serious health problems, including megaloblastic anemia (large, immature red blood cells), nerve damage (neuropathy), and cognitive issues. Early detection helps prevent complications and guides appropriate treatment, such as dietary changes, vitamin supplements, or injections.

Short name

B12 Level

Frequently asked questions

What causes low vitamin B12 levels?
Low vitamin B12 levels can result from poor diet (e.g., vegan/vegetarian diets without fortified foods), conditions that affect absorption (like pernicious anemia or Crohn’s disease), or certain medications (e.g., proton pump inhibitors). Chronic kidney disease or excessive alcohol use may also contribute.
What symptoms might I experience if my vitamin B12 is low?
Symptoms of low vitamin B12 may include fatigue, weakness, pale or yellowish skin, numbness or tingling in hands/feet, balance problems, memory loss, or mood changes. Some people have no symptoms until deficiency is severe.
How is vitamin B12 deficiency treated?
Treatment depends on the cause. If due to dietary deficiency, increasing fortified foods or supplements may help. If absorption is impaired, doctors may prescribe oral supplements, injections, or nasal sprays. Lifestyle changes, like avoiding alcohol-heavy diets, can also support recovery.
  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 17, 2026. · Read our editorial policy