Ok, well, I'm guessing the first thing crossing your mind is, "It has EPHEDRA in it!" or something similar. For one thing, ephedra has to be treated like any other drug on the market. If you take too much it can make you sick or even kill you. If you don't take enough then it won't have an effect. The best advice is to follow the directions on the packaging and to discontinue use if you have any weird side effects. I, for one, am very sensitive to most things. If I have too much caffeine I break out in hives. I have to be extremely careful about what I put on my face or I will have acne everywhere. But this product had no negative side effects on me whatsoever. I did only take one dose however. The Hydroxyslim bottle suggests taking 2 caplets twice a day with meals. I only took 2 caplets at breakfast time and the energy boost lasted ALL day. I sometimes have difficulty sleeping so I didn't take anymore which is a good thing because I probably wouldn't have been able to sleep.The energy boost is similar to that of having natural energy. I can't say it's like caffeine because it's not. I didn't have any anxiety or heart palpitations or anything. I just felt less tired - which is a miracle since I have hypothyroidism and I'm tired ALL the time. After a few days Hydroxyslim also gave me a mood boost. I'm normally too tired to exercise at all. With this I was able to exercise more and I felt better about myself. I've only been on the pills for a week and I've lost 2 pounds.I have heard from other users though that a person can become aclimated to Hydroxyslim and you have to cycle off of it for awhile. So I'm planning on using it for 90 days and then switching over to something else for 90 days and then switch back. I've heard this works for a lot of people so I will let you know how that goes. Also, you'll want to have plenty of water on hand when you take these. They make you very energetic and so you get thirsty more.