Vitamin B12 (Free) in Serum or Plasma
This test measures the amount of free (unbound) vitamin B12 in your blood. Vitamin B12 is essential for nerve function and red blood cell production.
["Free vitamin B12 helps assess your body’s vitamin B12 status and potential deficiencies, especially important for nerve health."]
Key facts at a glance
- LOINC
- 49115-9
- Short code
- Vit B1 free Bld-mCnc
- Synonyms
- Vit B1 free Bld-mCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- 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 This Test Is Done
Your healthcare provider may order this test if you have symptoms like numbness, tingling, fatigue, or weakness that could be linked to vitamin B12 deficiency. It may also be used to monitor vitamin B12 levels in people with conditions like pernicious anemia, malabsorption disorders, or those on certain medications that affect vitamin B12 absorption.
What to Expect Before the Test
No special preparation is usually needed. You may have a blood sample drawn from a vein in your arm. If you’re taking medications that could affect vitamin B12 levels, let your provider know.
What the Results Mean
Results can help determine if your vitamin B12 levels are too low, normal, or high. Low levels may indicate deficiency, while high levels could be due to certain medical conditions or lab artifacts. Your provider will interpret results in the context of your symptoms and overall health.
Common Conditions Linked to Vitamin B12 Deficiency
Vitamin B12 deficiency can cause nerve damage, anemia, and other health issues. Conditions that may increase risk include poor diet (e.g., vegan diets), stomach disorders (like atrophic gastritis), or conditions that interfere with absorption (e.g., Crohn’s disease).
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free vitamin B12 testing is particularly useful for diagnosing deficiencies in people with conditions that affect intrinsic factor (a protein needed for absorption) or those who have had stomach surgery. It can also help differentiate between intrinsic factor deficiency and other causes of low vitamin B12 levels, such as dietary insufficiency alone.
Short name
Free Vitamin B12
Frequently asked questions
What causes vitamin B12 levels to be measured as free?
How is free vitamin B12 different from total vitamin B12?
Can diet alone cause low free vitamin B12 levels?
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