i took clen before, i had the .4 mcg, the only problem i ever had ver were the following and i was taking 5 a day, i got warm, body heat elevated, i felt no heart problems at all no palpitations or anything keep in ming side effcts vary with everyone as we all know. And last i got muscle cramps prety bad, but that was my fault for not driking enough h2o that day other than that all good, i will continue to take it....i didnt even get blood pressure