Folate
What it measures, and what changes the number.
Folate, also called vitamin B9, is a B vitamin needed to make DNA and to produce red blood cells. Folic acid is the synthetic form. The test usually measures folate in serum, though some labs measure it inside red blood cells, which reflects longer term status.
It is commonly ordered with vitamin B12, since both are needed for red cell production and they are often assessed together, and it is read alongside the full blood count, especially MCV and hemoglobin.
Serum folate reflects recent intake, so labs often ask for a fasting sample. Hemolysis in the tube can raise serum results because red cells contain much more folate than serum. Labs may print it as Ácido Fólico (Vitamina B9).
Often read alongside: Vitamin B12, MCV, Hemoglobin, Red blood cells, Ferritin