I do have to agree with the above. I did some calculations and the amount of caffine you will get is a lot less than you would get from say an energy drink. If you are sensitive to caffine then it might work, but for myself (a caffine junkie) I didn't really feel anything. Also, the gunk in the Green Cow flavour became very annoying. It is however a really nice flavour, and I was vaping it day in, day out, for quite a while.