Jack3d is a pre-workout energy booster that users say gives them an intense focus during training, allowing them to train harder for longer.
It contains DMAA, dimethylamylamine, which increases the heart rate and is often used as a dietary fat burner.
The manufacturer USPlabs advises users to only take one scoop pre-workout and to not use it more than five days in every seven.
However, the body develops a tolerance to the supplement over time so people take more to get the same effect.
Side effects include nausea, dizzyness, insomnia if taken in the evening, slurred speech, and heart palpitations that could potentially lead to a heart attack. Many users also report a "crash" after the effects wear off.