I've taken 150mcg 1st thing in the morning on an empty stomach with no problems twice before (2 weeks each time). However, I got chastised from a friend/vet who was certain that I was going to do damage to my heart this way. He told me although T3 has a long half-life, it still enters your system all at once. This didn't make sense to me at the time but if I compare it to clen which also has a long half-like. I can't handle more than 40mcg of clen at one time. I get the shakes to bad. So I'm forced to break my clen dose up during the day to get to 120mcg. Maybe the same also applies to T3.