Elove, whether it's safe or not will depend on the individual and their health - all ECA or EC stacks (such as ripped fuel, hydroxycut, stacker II etc) will have extensive warnings and should be followed. If you don't have any of the pre existing conditions mentioned in the warning then taking the product as directed should be OK. Should be OK. Some find they just can't handle the side effects - and feeling jittery is one of them.

What is often suggested is taking half the dose for the first few weeks until you get used to the product. There is a huge thread stuck at the top of this forum on Thermogenics that lists all the pros and cons of these products along with a lot of questions and answers from members such as yourself.

HTH
Nat