Cytomel (T3) Side Effects


Cytomel (T3) is generally well tolerated by most users, and side effects are mostly associated with overdose of the hormone. The most prominent (and desired) T3 side effects happens to be the increase in body heat output as a result of Cytomel’s ability to increase total body metabolism. Through the increase in metabolic rate via the production and consumption of energy in the body, a greater amount of heat output occurs that can normally be monitored with the use of a personal thermometer. The reason as to why this particular Cytomel side effect is desired by athletes and bodybuilders is because it serves as a very strong indication that this compound is indeed doing its job in increasing metabolic rate. If there is absolutely no increase in the overall body temperature from the use of T3, it is a strong indication that something is wrong – either the product is fake, the dose is too low, or there is a problem at the cellular level in regards to the proper functioning of T3 (please see the details in regards to Cortisol and L-Carnitine use with T3 under the Cytomel (T3) Cycles section of this profile for more details).

The manner in which body temperature is measured with T3 use involves the athlete or bodybuilder monitoring their temperature for several days prior to beginning T3 use. This involves taking body temperature immediately upon waking up in the morning, and during the day while at rest (not taken near periods of strenuous physical activity). After a few days of temperature monitoring, an average is taken. When beginning T3 use, body temperature is observed again starting from the first day of use in the same manner (temperature taken immediately upon arising and then once again later on in the day). Temperature increases as a result of the metabolic boosting effects of Cytomel (T3) should not be dramatic, but merely an increase in a degree or two above the normal average temperature recorded while the user was not administering T3. Increases well beyond a degree or two to the point of uncomfortable feverish temperature would indicate a serious problem (thyroid storm) and medical help should be sought immediately.


Aside from body temperature increases, a common Cytomel side effect can include increased heart rate and/or irregular heartbeat. It is important to understand that T3 is not a stimulant, and does not exhibit any stimulant-like effects on the body. There are no tremors, shaky hands, anxiety, or any other stimulant-like side effects that should be associated with T3 use. However, some individuals have reported increased heart rate during T3 use, and at particularly higher dosages, heart palpitations. This is due to the fact that T3 is an essential mediator of heart rate regulation, and this is not because of any stimulant effects. Normally, these T3 side effects on heart rate and heartbeat are associated with very high T3 doses.

Other more rare Cytomel side effects (often associated with overdose) includes: headaches, irritability, sweating, nervousness, irregular heartbeats, menstrual irregularities, and increased bowel movements. Acute overdose of T3 can be life threatening.