I used to for a very short time. I drink a large container of coffee every morning, and for about two weeks I drank a couple of Red Bulls in the afternoon. I went to my doctor with a racing heart, and he asked about my caffeine consumption and then advised me to either give up the Red Bull or the coffee. I gave up the Red Bulls, and everything was fine after that. I tried going no caffeine at all about a year or two ago, but I missed the coffee so I brought that back in.