The folate (vitamin B9) test measures the level of this vitamin in the blood to assess for deficiency or abnormal elevation. Folate plays a vital role in DNA synthesis, cell division, and the production of healthy red blood cells. This test is typically ordered when symptoms such as fatigue, weakness, pallor, or signs of megaloblastic anemia (such as enlarged red blood cells) are present. It is also commonly performed during pregnancy to ensure adequate folate levels, which are essential for preventing neural tube defects in the fetus. The test usually requires a fasting blood sample, and results are interpreted in nanograms per milliliter (ng/mL). Low folate levels are often due to poor diet, malabsorption (such as in celiac disease), alcoholism, or the use of certain medications (like methotrexate). Elevated folate levels are usually caused by supplementation or consumption of fortified foods. It is important to note that folate and vitamin B12 deficiencies can present with similar symptoms, so physicians often test for both simultaneously, as treating one deficiency without addressing the other may lead to serious neurological complications.