I tried it recently, starting out with 200 mg. It felt pretty neutral for the first few hours, "maybe" feeling a modest increase in energy. But as the hours went by going into the evening, I began to notice a very unsettled feeling. It was so far removed from having taken it in the morning, that I was certain it was cause and effect. It lingered the following day as well.
I decided to "pause" and wait before trying it again. A few days later, I tried 100 mg. Within a short amount of time, I began to have that unsettled feeling again, so was able to connect the dots of my first experience. It was so uncomfortable, that I decided to return it on Amazon.
At first they said that as a supplement, they couldn't return it and receive a refund. So I called Amazon customer service directly, and they promptly gave me a refund, and said to not send it back. Do whatever I want with it. Not sure what I'm going to do at this point. Wanted to mention the Amazon customer service experience as I've always had good results calling them directly. 888-280-4331