Normally there are many sources of folate in food, including for vegans, but certain medications, some unavoidable, cause deficiencies. (nutritionfacts.org)
Grain products are fortified with folic acid (the synthetic form of folate). (babygourmet.com)
Recent folate intake from foods can greatly affect the blood folate levels, which may therefore not be the best indicator of the adequate amount of folate in the body. (nutrientsreview.com)