letrozole has a half life of roughly 2 days so it doesn't matter. I assume you are taking letro for gyno symptoms, yes? Don't mean to be harsh dude, but seriously, all I did was google letrozole half-life and I figured it out. You MUST do your research. This will prevent gyno in the future and help you properly employ supplements/gear. If you just jump in without research you'll hit some rough consequences, as you've seen.