T3 works by giving you more thyroid Hormone, which will elevate your metabolism and base body temperature. That is how it helps you to burn fat. Basically, you are putting yourself into a hyperthyroid state. Problem is, that it can raise you blood pressure, as well as your heart rate. However it works great when stacked with Clenbuterol. I run both low dose, at apporx 25-50mcg, T3 for 6 weeks, Clen 2 weeks on 2 weeks off.