TwinLab Tribulus Fuel Tribulus Terrestris Extract, Capsules, 100-Count Bottles (Pack of 2)

I've only taken this supplement for a few days, so I really cannot comment on whether it has any effect on testosterone levels (as evidenced by any physical measures). I can say, however, that it makes my breath stink really bad for the first couple of hours after I take it. Given that the recommendation is to take it with the morning meal (which, for me, means that my breath stinks while I'm working out at the gym and breathing heavily -- not nice) and in the evening, presumably when one is more likely to be able to have intimate relations -- another not good time to have stinky breath.