Vitamin B12
Vitamin B-12
- Sample
- Blood
- Usual units
- pg/mL
Also known as Vitamin B-12 · B12 · Cobalamin · Cyanocobalamin · Vit B12 · Serum Vitamin B12
What this test measures
Vitamin B12, also called cobalamin, is a vitamin the body uses in DNA production, red blood cell formation, and nerve cell function. A blood test measures the total B12 circulating in blood, most of it bound to carrier proteins, giving an overall reading of how much is present. It is usually reported in picograms per milliliter (pg/mL).
Reading your report
There isn’t one standard range for this test — each lab prints its own. Use the range shown next to your result.
Vitamin B12 unit converter
Convert Vitamin B12 units
Labs print this test in pg/mL or pmol/L depending on where the sample was run.
Related guides
- Guide
Why the same blood test has different "normal" ranges at different labs
Reference intervals are built from each lab's own population and equipment, which is why two labs can print different ranges for the same sample.
- Guide
Reference interval, cutoff, and the "optimal" numbers online: three different things
The range beside your result, the target a website quotes, and the threshold that defines a condition are built in different ways and answer different questions.
- Guide
Why the same lab printed a different reference range for you this year
Ranges are not fixed constants. The lab can change method, revise its reference group, or apply a range that depends on your age — none of which is an error.
- Guide
Vitamin B12 and Active B12: two different tests with similar names
A total B12 measures all of it in circulation; Active B12 measures only the fraction available to your cells. They are not interchangeable, and reports rarely say which you had.
- Guide
µ and μ are different characters, and lab software often disagrees about which one it used
Two visually identical characters sit behind the µ in µg/dL. Software treats them as different, which is why a unit can fail to match itself between two reports.