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Vitamin B12 (Cobalamin) with Serum Concentration Measurement

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

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

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
8013-5
Short code
RUBV Ab Ser-aCnc
Synonyms
RUBV Ab Ser-aCnc
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 healthcare provider may order this test if you have symptoms like fatigue, weakness, numbness, or tingling in your hands and feet. It may also be recommended if you have conditions like pernicious anemia, gastrointestinal disorders, or if you follow a strict vegetarian or vegan diet, which can reduce vitamin B12 intake.

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 instructed by your provider, but this is not always required for this specific test. Bring any medications you’re currently taking to your appointment.

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 Possible Results?

Results are typically reported as a concentration value in picograms per milliliter (pg/mL) or other units. Your doctor will compare these results to your individual reference range to determine if your levels are within a healthy range or if further action is needed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B12 (Serum)

Frequently asked questions

What causes vitamin B12 deficiency?
Vitamin B12 deficiency can result from poor dietary intake (e.g., vegan/vegetarian diets), conditions affecting absorption (like pernicious anemia or Crohn’s disease), or certain medications that interfere with absorption. Chronic conditions like kidney disease or alcohol use may also contribute.
What symptoms might indicate low vitamin B12?
Symptoms may include fatigue, weakness, pale or yellowish skin, shortness of breath, numbness or tingling in hands and feet, dizziness, or memory problems. Some people have no symptoms at all, especially if deficiency is mild.
Can vitamin B12 levels be affected by medications?
Yes, certain medications like proton pump inhibitors (for acid reflux), metformin (for diabetes), or antacids can reduce vitamin B12 absorption. Always discuss all medications with your doctor, as they may need to adjust your vitamin B12 levels accordingly.
  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