Trusted-source health topic
Vitamin B12
Vitamin B12 is needed for healthy blood cells and nervous-system function.
Why is this important?
Understanding the purpose and limits of laboratory information can support a more informed conversation with a qualified healthcare professional.
How laboratory testing relates
A B12 result may be considered with blood-count findings, symptoms, nutrition, medicines, and additional laboratory tests. One result does not identify a cause by itself.
Before testing
Preparation is test-specific. Follow the instructions given for the exact test and contact the laboratory if fasting, timing, medicines, or specimen collection is unclear. Do not stop medicines unless a qualified professional tells you to.
Educationally related laboratory guides
These links explain related laboratory records. They are not recommendations to request or purchase a test.
Sources & further reading
- MedlinePlus, U.S. National Library of Medicine: Vitamin B Test
External authoritative patient reference · Verified 2026-08-10