Vitamin B12
Measures vitamin B12 levels to detect deficiency that can cause anemia, nerve problems, and fatigue.
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LevelPanel has no business or affiliate relationship with Quest or LabCorp. These links are provided as a public service.
Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
What this test measures
This test determines the concentration of vitamin B12 (cobalamin) circulating in the blood. B12 is a water-soluble vitamin that the body cannot manufacture on its own; it must come from dietary sources, primarily animal products like meat, fish, dairy, and eggs, or from supplements. Once consumed, B12 requires a specialized protein called intrinsic factor, produced in the stomach lining, in order to be absorbed in the small intestine.
Inside the body, B12 serves as a cofactor for enzymes that drive DNA synthesis, fatty acid production, and the formation of myelin, the protective sheath surrounding nerve fibers. It is also essential for healthy red blood cell development. When B12 is deficient, a compound called methylmalonic acid accumulates in the blood because the enzyme that normally converts it (methylmalonyl-CoA mutase) cannot function without adequate B12. Identifying a deficiency early matters because prolonged shortage can lead to irreversible nerve damage and a type of anemia characterized by abnormally large red blood cells.
Who should consider this test
You might consider this test if you are experiencing any of the following:
- Individuals following vegetarian or vegan diets, as B12 is primarily found in animal products
- Adults over 60 years old, who may have reduced ability to absorb vitamin B12 from food
- Those with digestive disorders such as Crohn's disease, celiac disease, or pernicious anemia that affect nutrient absorption
- People experiencing symptoms like fatigue, weakness, pale skin, numbness in hands or feet, or memory problems
- Individuals who have had gastric surgery or take medications that reduce stomach acid production
- Those with a family history of pernicious anemia or autoimmune conditions
What to expect
Preparation
Fasting for 6-8 hours before the test may be recommended by some providers, though it is not always required. Individuals should inform their healthcare provider about any medications or vitamin B12 supplements they are taking, as these may affect test results.
Sample Type
A standard blood sample drawn from a vein, typically from the arm.
Collection
A healthcare professional will insert a needle into a vein and collect blood in an air-tight vial or syringe. The procedure is quick and involves minimal discomfort.
Turnaround
Results are typically available within 1-3 business days after the laboratory receives the sample.
Understanding your results
Results are typically expressed in picograms per milliliter (pg/mL) or picomoles per liter (pmol/L), with normal values generally falling in the range of 160 to 950 pg/mL, though laboratory-specific cutoffs can vary. Levels at or below the low end of the range may indicate deficiency, while very high readings can occur with certain liver conditions or supplementation. Healthcare providers interpret B12 results in combination with symptoms, dietary history, and sometimes additional markers like methylmalonic acid or homocysteine to build a complete picture of B12 status.
| Population | Reference Range | Notes |
|---|---|---|
| Adults | 160-950 pg/mL (118-701 pmol/L) | General reference range; some laboratories may use slightly different ranges |
| Borderline | 200-300 pg/mL (148-221 pmol/L) | May require additional testing or monitoring |
Reference ranges shown are general guidelines. Your lab report will include the specific reference range used by the laboratory that processed your sample, which is the authoritative range for interpreting your results.
What does a “Low” result mean?
Levels below 160 pg/mL (118 pmol/L) may indicate vitamin B12 deficiency, and individuals with this degree of deficiency are likely to have or develop symptoms. Results between 200-300 pg/mL are considered borderline and may require additional testing. Low B12 levels may suggest vitamin B12 deficiency, pernicious anemia, or an overactive thyroid. Deficiency should often be confirmed by checking methylmalonic acid levels, as elevated MMA indicates true B12 deficiency.
What does a “High” result mean?
Increased vitamin B12 levels are uncommon, as excess vitamin B12 is typically removed through urine. Abnormally high levels (over 900 pg/mL) may suggest underlying conditions such as liver disease, kidney problems, diabetes, or certain forms of leukemia. While elevated B12 levels are generally rare and usually not concerning, extremely high levels warrant evaluation by a healthcare provider to assess for underlying conditions.
Privacy & confidentiality
All test orders are authorized and results reviewed by an independent, board-certified physician who is not the patient's personal doctor. Your vitamin B12 test results are completely confidential and handled with the utmost privacy. Results are <u>not reported to your doctor</u> unless you choose to share them, and they are <u>not part of your medical records</u> maintained by your healthcare provider. The test results will <u>not appear on insurance statements</u> or explanation of benefits (EOB) forms, ensuring your privacy is fully protected. We understand that some individuals prefer to monitor their health markers privately before discussing them with their healthcare provider. Your test information is never shared with employers, insurance companies, or government agencies. All results are delivered securely through your confidential online portal, accessible only with your login credentials. This private testing approach allows individuals to take control of their health monitoring with complete discretion and peace of mind.
Frequently asked questions
Related tests
Folate Test
Often tested together with B12 as both vitamins are involved in similar metabolic processes and deficiencies can cause similar types of anemia
View TestComplete Blood Count (CBC)
Can detect megaloblastic anemia and other blood abnormalities that may result from vitamin B12 deficiency
View TestComprehensive Metabolic Panel (CMP)
Provides additional information about liver and kidney function, which can be affected by or contribute to vitamin B12 abnormalities
View TestRelated conditions
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Read ArticleLast reviewed: April 2026
CPT Code: 82607
This test may not be available in: NY, NJ, RI
This page is for informational purposes only and does not constitute medical advice. Always consult with a healthcare provider regarding any health concerns. LevelPanel does not diagnose, treat, or prescribe.
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LevelPanel has no business or affiliate relationship with Quest or LabCorp. These links are provided as a public service.
Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
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