I have been taking letrozole for 6 months. When I take the full dose I often have abdominal pain, nausea and heartburn...wakes me up in middle of the night. If I take half a dose I have no side effects. My oncologist says there are no studies for the effectiveness of half a dose so he does not support it. He says nausea and heartburn are not side effects of letrozole thus he referred me to a gastroenterologist. I have had several tests and my insides are fine. I am following a GERD diet but still experience digestive issues when I try to go back to full dose of letrozole. May be trying exemestane In the future as it it is the only one I have not been prescribed. My digestive issues were worse on Tamoxifen. Also was diagnosed with gastritis then. Again, could not tolerate full dose of Tamoxifen but did fine with half dose. It is so hard to know the right thing to do. Hoping you get some answers and will stay in touch.