Biomarker · Nutrition
Vitamin B12 (cobalamin)
Vitamin B12 is needed for red blood cells and nerve function. Learn what a B12 blood test shows, who is at risk of low levels and what affects results.
Written by LON6EVITY Editorial Team · Last updated
Overview
Vitamin B12 helps the body make healthy red blood cells and keeps nerves working normally. The body cannot make it, so it comes from food — mainly animal products — or supplements.
Why it matters
MedlinePlus notes that low B12 can cause a type of anaemia and nerve problems such as numbness or tingling. People following vegan diets, older adults and people with some digestive conditions or taking certain medications are more likely to have low levels.
Interpreting results
Blood B12 does not always reflect levels inside cells. When results are borderline, clinicians sometimes add tests such as methylmalonic acid or homocysteine.
How the test is performed
A blood sample; you may be asked to fast for several hours.
Reference ranges
Reference ranges and targets differ between laboratories, units and guidelines, and depend on age, sex, method and your overall clinical picture. A single result is not a diagnosis — interpret it with a qualified clinician.
Factors that can affect the result
- Vegan or vegetarian diet
- Older age
- Metformin and acid-reducing medication
- Digestive conditions
- Supplements
Questions people commonly ask
- Can I have B12 deficiency with a normal result?
- Occasionally. Borderline results may need additional tests chosen by your clinician.
Related biomarkers
Related topics
Understand your biomarkers in context
What does this mean for your own health data? Log your results, follow trends over time and bring an organised summary to your next doctor's appointment.
Sources
- Vitamin B Test. MedlinePlus, U.S. National Library of Medicine.