Folic acid tablets have few side effects, rare allergic reactions, and gastrointestinal symptoms such as nausea and bloating may occur with long-term use. When large amounts of folic acid are taken, it can make the urine yellow. Folic acid tablets are a water-soluble B vitamin that can reduce the incidence of fetal neural tube malformations when taken during the period of preparation for pregnancy through the first 3 months of early pregnancy. Overdose of folic acid tablets can also produce many adverse effects, the more common of which are gastrointestinal symptoms such as anorexia, nausea, vomiting and bloating. Taking large amounts of folic acid can also turn urine yellow and occasionally cause allergic reactions, with common symptoms including itchy skin, discomfort, swelling, and dizziness. Megaloblastic anemia caused by vitamin B₁₂ deficiency cannot be treated with folic acid alone.