Patients taking methotrexate may experience unpleasant side effects and are most likely to discontinue treatment for that reason.[5] Concurrent administration of folic acid or folinic acid may reduce the occurrence of more intolerable side effects, such as stomatitis, nausea, diarrhea, and alopecia.[5] The most frequently encountered adverse reaction is an elevation in liver enzymes, so frequent monitoring is critical.[5] Because of the teratogenic effects of methotrexate, it is recommended that women of child-bearing age use a reliable method of birth control.[5]