I have been on Letrozole since Dec. 05,2018. Have noticed some side effects. I am having more recurring headaches normally I might have 2 or 3 headaches in a year. Also I am a pretty laid back person but I find I get agitated quickly over what I would consider minor happenings. Anyone have problems with constipation or diarreha. Have had a bought with constipation (bowel blockage and flare up of Diverticulitis. Don’t know if that was just a happening or side effect of Letrozole.