Beware!!!! I used it in the form of Ma Huang (herb). I started having dizzy spells, but never associated it with the supplement. It was helping me lose weight and I had lots of energy. I went to the dr when I started passing out - he thought it might be blood sugar problem. I had alot of horrible tests and nothing showed up. Finally, he asked me what supplements I was taking. I told him about the herbs I was using. He told me that ephedra could cause seizure, stroke, heart attack, and a whole list of other nasty things. I stopped taking the herb and within a week I was back to my old self - no more dizzy spells, heart palpatations, or fainting. I consider myself lucky - since then I've done some research and discovered people have died while using the supposedly safe all-natural supplements containing herbal ephedra.