Short answer: Vitamin B12 (cobalamin) and folate (vitamin B9) are B vitamins needed to make red blood cells and DNA; B12 is also needed for the nervous system. The blood tests measure how much of each circulates. They are often ordered together and read with the complete blood count, especially when red cells are larger than usual.
At a glance
| Measures | Vitamin B12 (cobalamin) and folate (B9) in the blood |
|---|---|
| Units | pg/mL or pmol/L for B12; ng/mL or nmol/L for folate |
| LOINC | 2132-9 (B12), 2284-8 (folate) |
| Ordered for | Anaemia with large red cells, tiredness, nerve symptoms, vegan diets, some medicines |
| Read with | The complete blood count |
| Keep | Values, units and dates, especially during supplementation |
What the test measures
B12 comes from animal foods and some fortified foods; absorbing it needs a protein made in the stomach (intrinsic factor). Folate comes from vegetables, legumes and fortified foods. Low levels of either can cause large red cells (a high MCV on the blood count).
Because blood B12 does not always reflect what reaches the tissues, doctors sometimes add other tests (for example methylmalonic acid or homocysteine).
When it is ordered
Common reasons, which your doctor adapts to you:
- when a blood count shows anaemia with large red cells;
- when tingling, numbness, memory or mood changes need checking;
- in people at risk: strict vegan diet, older age, stomach or bowel conditions, some medicines (for example metformin or acid-reducing medicines).
How the result is written on the report
| Result on the report | LOINC code | Usual unit | Also seen as |
|---|---|---|---|
| Vitamin B12 | 2132-9 | pg/mL | pmol/L (×0.738) |
| Folate (serum) | 2284-8 | ng/mL | nmol/L (×2.266) |
| MCV (often on the same report) | 787-2 | fL | — |
B12: pmol/L = pg/mL × 0.738 (400 pg/mL ≈ 295 pmol/L). Folate: nmol/L = ng/mL × 2.266 (10 ng/mL ≈ 22.7 nmol/L).
Reading your report
Results near the lower limit are a grey zone, and the range differs between labs, so doctors interpret them with the symptoms and other tests. Taking B12 or folic acid supplements shortly before the test raises the result; tell your doctor what you take.
Keeping the results in your record
Scan or photograph the report in Anpheros Daily: each value is read with its unit and the laboratory's reference range, you check it, and it is stored with its LOINC code as an HL7 FHIR Observation, a format used by many hospitals and national health systems. Results from different laboratories line up on one chart over time, and the lab unit converter helps when two reports use different units. Our guide on how to read lab results explains reference ranges and flags in general; the lab results guide for a new doctor shows how to share them.
What this page does not do
It explains what the test is and how the result is written. It does not interpret your result, diagnose or recommend treatment: the meaning of a value depends on your history, your other results and how the sample was taken, and that is your doctor's job.
Related pages
Sources
Frequently asked questions
Why are B12 and folate tested together?
Both are needed to make red blood cells, and a lack of either can cause similar changes on the blood count.
How do I convert B12 from pg/mL to pmol/L?
Multiply by 0.738. For example, 300 pg/mL is about 221 pmol/L.
Can a normal B12 result miss a deficiency?
Sometimes. That is why doctors may add other tests when symptoms suggest it.
Do supplements affect the test?
Yes. Recent supplements raise blood levels. Tell your doctor or lab what you take.
Try it in Anpheros Daily
Photograph your lab report and Anpheros Daily lines up each value with its reference range, so you can compare reports from different laboratories.
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