Can blood tests for anemia give you wrong results?

Rarely: Detecting anemia (low hemoglobin / hematocrit) is one of the simplest of all lab tests, but clerical / computer errors still happen. If there is doubt whether you are anemic, repeat. Labs required to seek the cause (serum iron, b12, folate, (folic acid) reticulocyte count, many others) are usually reliable; taking an iron pill before the draw can mask elemental iron deficiency.