what is the half life of caffeine?

The half-life of caffeine, as mentioned by Andrew Huberman and discussed with guest Matthew Walker, is somewhere between five to six hours, and the quarter-life is about ten to twelve hours 1. This means that generally, after five to six hours, half of the caffeine ingested would have been metabolized by the body. However, individual variations exist, which can be attributed to differences in liver enzyme activity, notably those of the cytochrome P450 class that metabolize caffeine. These variations can make some people more sensitive to the effects of caffeine than others 1.