I've been taking 2.5mg of letrozole every day for the past week and I still feel like my estrogen is high. I'm taking it because my estrogen levels are high but other AI's such as Aromasin and Arimidex only seemed to help a little. Before taking letro I took 25mg Aromasin and 1mg of Arimidex per day for a week and it did almost nothing. I went with the "nuclear" option of 2.5mg letro daily, which is the dose prescribed to breast cancer patients, and I feel like my estrogen levels still haven't completely tanked. I'm still experiencing sides of high estrogen such as water retention and gyno flair up. Usually libido is destroyed from crashing estrogen but mine has stayed the same and may have even increased because it feels similar to when I was taking Proviron (it may be caused by letro increasing DHT and free test significantly). Am I just immune to AI medication? I've read accounts of people taking 1 pill of Aromasin, 1 time and it completely wrecks them and their E2 levels, so it's very surprising how I'm able to take 1 full pill of letro for a week and be fine. I doubt my AI is fake because I purchased them from different sources in the past.