When do symptoms of menstrual dysmenorrhea occur?

Menstrual dysmenorrhea is characterized by painful menstrual cramps. The pain may start a few days before the onset of menstruation and may continue for several days. It is usually most intense during the first few days of the menstrual period. The pain may be accompanied by other symptoms such as nausea, vomiting, fatigue, headache, and diarrhea.