The first time I took four capsules, because I'm a man and I dont read the full instructions, I've never sweated so much in my life, so the next time I took just one, an hour before my exercise, I had a great workout, no jitters, got my sweat on, felt great during and after, took it about 4pm and still had a good nights sleep, it seems to last about 2 - 3 hours, so I wouldn't plan on heading into the office afterwards, although this could change as my body gets used to it, overall very happy and...