Vitamin B12 (Serum or Plasma Concentration)
This test measures the amount of vitamin B12, an essential nutrient needed for healthy nerve function and red blood cell production.
["Your B12 levels help ensure proper nerve function and blood health."]
Key facts at a glance
- LOINC
- 61534-4
- Short code
- Vit B12 PhenX
- Synonyms
- Vit B12 PhenX
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 200
- Ref high
- 900
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- phenx
- 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 healthcare provider may recommend this test if you have symptoms like numbness, weakness, fatigue, or memory issues, or if you have conditions like pernicious anemia, gastrointestinal disorders, or poor diet. It may also be used as part of routine screening or monitoring for vitamin deficiencies.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for a few hours before the blood draw if your test involves a specific timing requirement. Bring any medications or supplements you’re currently taking to your appointment.
What the Test Involves
A healthcare professional will draw blood from a vein in your arm. The process is quick and typically painless. You may feel a slight pinch, but most people tolerate it well. The blood sample is then sent to a lab for analysis.
What the Results Mean
Results help determine if you have a vitamin B12 deficiency, which can affect how your body uses energy and maintains nerve health. Low levels may require dietary changes, supplements, or medical treatment to restore balance.
Reference range
NCBI: Vitamin B12 200-900 pg/mLN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low vitamin B12 levels can lead to anemia, nerve damage, and cognitive issues. High levels may indicate underlying conditions like liver disease or certain medications. Your provider will interpret results in the context of your symptoms and overall health.
Short name
Vitamin B12 Level
Frequently asked questions
What causes low vitamin B12 levels?
What are common symptoms of low vitamin B12?
How is vitamin B12 deficiency treated?
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 17, 2026. · Read our editorial policy