"Never got used to drinking coffee, my stomach could not really stand it and energy drinks did only go so long before their side effects started to kick in and affect my health. After the age of 25 I found myself being so mentally tired all the time and would take several hours to fully awake no matter how many hours I slept. I tried a travel size pack of Vivarin once at work and felt the difference right away, after only 10 minutes I was able to concentrate and finish what used to be my 2 hour paperwork in about 30 minutes. Have not had any side effects when I take it as it is described and there was no boost limit since it only woke me up! I would not recommend taking more than two pills at once or with any other caffeine product though!"