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Vitamin B12 (Cobalamin) Level

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 red blood cell production, nerve function, 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
4203-6
Short code
Cyanocobalamin PO Dose
Synonyms
Cyanocobalamin PO Dose
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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, weakness, numbness, or tingling in your hands and feet. It may also be done to check for vitamin deficiencies, especially in people with conditions like pernicious anemia, celiac disease, or those who don’t absorb nutrients well from food.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if your blood is drawn from a vein, but if it’s drawn from your finger, fasting isn’t required. Bring a list of medications you’re taking, as some can affect results.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm using a small needle. The process takes a few minutes, and you may feel a brief pinch. The blood sample is then sent to a lab for analysis.

What Are the Results?

Results are typically reported as a concentration of vitamin B12 in the blood. Low levels may indicate a deficiency, while very high levels (rare) could signal other conditions like certain cancers or liver disease. Your doctor will interpret the results in the context of your symptoms and medical history.

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 levels can result from poor diet (e.g., vegan/vegetarian diets lacking fortified foods), malabsorption issues (like pernicious anemia or celiac disease), or conditions that affect the stomach or intestines.
What Are the Symptoms of Low Vitamin B12?
Symptoms may include fatigue, weakness, pale skin, numbness or tingling in hands/feet, dizziness, memory problems, or mood changes. Some people have no symptoms until the deficiency is severe.
How Is Vitamin B12 Deficiency Treated?
Treatment typically involves vitamin B12 supplements (oral, injections, or nasal sprays) to restore levels. Lifestyle changes, such as eating fortified foods or taking supplements, may also help if diet is the cause. Follow-up tests are often needed to monitor progress.
  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