It depends on how much fat you have to lose, and how much muscle you have already. If you are on gear then go ahead with no problem. If you are not then you might want to think about it because you will lose a lot if you go to heavy on the T3. I did two cycles of T3 once and was not on gear, and the first was fine because I took a low dose and lost a mostly BF, but the second weakened me and I lost way way too much muscle-- I was pissed but I was also stupid for doing them so close together. It is easy to want to overdue T3 when you have a lot of BF to lose, or think you do. But we learn the hardway from mistakes.
If you are going to take it w/o AAS, just use it to kickstart your metabolism. 25mcg is best - 50mcg at most and only use it for a month to six weeks-NOTHING MORE! and stay off for the same amount of time as the cycle, but preferably longer. It works really well with thermorexin or ECA. One last thing cycle up and taper down the same way at the end. Run the Thermorexin/ECA two weeks past the T3 to avoid any kind of crash and stay off both for a while. My best result was T3 with ECA for 1 month then another two weeks of ECA afterwards. My metabolism stayed going for sometime after without anything in my system and I continued to lose BF. Good Luck!