Vitamin B12 (Serum or Plasma Concentration)
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.
["Check your vitamin B12 levels if you have symptoms of deficiency or need monitoring for conditions affecting absorption."]
Key facts at a glance
- LOINC
- 10419-0
- Short code
- Trans Fact VIII Vol Patient
- Synonyms
- Trans Fact VIII Vol Patient
- 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 This Test Matters
Vitamin B12 is crucial for maintaining healthy red blood cells, nerve function, and DNA production. Low levels can lead to anemia, neurological issues, or other health problems. This test helps identify whether your body isn’t absorbing enough vitamin B12 or if your diet lacks it.
Common Reasons for Testing
Your doctor may order this test if you have symptoms like fatigue, weakness, numbness in hands/feet, balance problems, or unexplained anemia. It’s also recommended for people with conditions like pernicious anemia, celiac disease, or those on long-term vitamin B12 supplements.
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 blood draw if your lab requires it. Wear a comfortable shirt for easy access to your arm.
During the Test
A healthcare professional will insert a small needle into your arm to draw blood. You may feel a slight pinch, but it usually takes only a few minutes. The blood sample is then sent to a lab for analysis.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low vitamin B12 levels can cause anemia (reduced red blood cells), nerve damage, or cognitive issues. High levels are less common but may indicate overabsorption or certain medical conditions. Your doctor will interpret results in the context of your symptoms and medical history.
Short name
Vitamin B12 Level
Frequently asked questions
What does a low vitamin B12 level mean?
Can vitamin B12 levels change over time?
Are there any risks or side effects from this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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