Wait for as long as your menstrual period normally stops you, and then take a ritual bath

One of the female Companions complained to the Prophet (may Allah's peace and blessings be upon him) about experiencing an incessant flow of blood. He ordered her to stop praying for as long as her menstrual period normally prevented her from praying before experiencing that new situation; then, she should take a ritual bath and pray. So, she used to take a ritual bath voluntarily before each prayer.