for the first 2 days i tried it, i took 2 scoops. it was so strong i would get winded after my first warm up sets because my heartrate would elevate so much. i wouldnt be surprised if i was throwing out some crazy arrythmias, too. my stim tolerance is through the roof... tried one scoop today and didnt feel like i was going to stroke out, so id HIGHLY recommend starting out slow with this stuff. that is all.