Folic acid has an effect when you take too much of it, and there will be adverse reactions. 1. Reduce the seizure threshold: high-dose folic acid can antagonize the antiepileptic effect of phenobarbital, phenytoin sodium and paracetamol, which can significantly reduce the seizure threshold and increase the number of seizures in sensitive patients. 2. Influence the absorption of zinc: oral administration of large doses of folic acid can affect the absorption of trace elements of zinc. 3. Gastrointestinal symptoms: too much folic acid may cause nausea and vomiting, loss of appetite, intestinal flatulence and other symptoms, and urine is yellow. Small doses of folic acid help prevent fetal neurodevelopmental disorders and are generally taken in preparation for pregnancy and early pregnancy, and should be taken according to the instructions or as prescribed by the doctor to avoid adverse effects on health. Patients who need to supplement folic acid are advised to go to a regular hospital and use it under the guidance of a doctor.