Norethisterone has shown to work for controlling heavy or painful bleeding and symptoms of endometriosis. When treating heavy periods, Norethisterone was shown to reduce bleeding by 87%
. For people with endometriosis, using Norethisterone for six months reduced the abnormal growth causing their pain and bleeding by 37.2%
In a clinical trial of women looking to delay their periods, Norethisterone was much more effective than the combined pill. Only 8% of women in the Norethisterone group had a small amount of spotting, compared to 43% of women on the combined pill. The women taking Norethisterone also preferred their treatment and were more likely to recommend it.