T-3 or Cytomel is not an anabolic steroid, it is a thyroid hormone. T3 speeds up the metabolism causing a faster conversion of carbohydrates, proteins and fats.
The result is increased fat burning and T3 simultaneously makes the steroids more effective, probably because of the faster conversion of protein. T3 is usually used as a part of cut (dieting) cycles, it works especially good with Primobolan, Winstrol, Anavar, Masteron, Clenbuterol and Proviron.
As for the dosage, one should be very careful since Cytomel is a very strong and highly effective thyroid hormone. It is extremely important that one begins with a low dosage, increasing it slowly and evenly over the course of several days. Most athletes begin by taking one 25 mcg tablet per day and increasing this dosage every three to four days by one additional tablet. A dose higher than 100 mcg/ day is not necessary and not advisable.
Our experience is that most symptoms consist of trembling of hands, nausea, headaches, high perspiration, and increased heartbeat. These negative side effects can often be eliminated by temporarily reducing the daily dosage.
Source : www.xtrememuscle.net