One dangerous symptom of endometriosis is excessive bleeding during menstruation. Menstruation may also last for longer than 7 days. Excessive bleeding can cause low levels of iron. This can lead to fatigue, hair loss, and anemia. For women who experience heavy or long menstruation, iron supplements or iron intravenous injections may be necessary. Taking birth control regularly can help women with endometriosis. Continuous use of birth control without breaks can reduce the number of periods, which can remove this symptom in entirety.