Dude at least be specific before just blurting out 'it will fuck you up'. Bottom line is - educated yourself and learn what the doseages are. The white is .2mg - 10x the strength of regular clen. The yellow (not made any more because a dangerously high doseage if taken haphazardly) was .5mg - 25x strength regular clen.
Either one will "fuck you up' if you dont know what your are doing. Its the not knowing what youre doing that will fuck you up!