For the former, coffee researcher Joseph Rivera, the founder of Coffee Chemistry, suggests reducing your intake by half for a few days, then halving that for a few more days, and so on. “After about a week you should be pretty much back to how you were without drinking caffeine,” he says.

Why does caffeine stop working?

As adenosine binds to its receptors, drowsiness sets in. At first, caffeine might be able to block those receptors, preventing performance declines. But as sleep debt mounts, caffeine fails to keep up with the buildup of adenosine, its receptors or both.

Does caffeine ever stop working?

Once in the body, caffeine will persist for several hours. In fact, it takes about six hours for half of the caffeine to be eliminated, according to the National Sleep Foundation. But, as the study discovered, relying on caffeine long term doesn't negate the effects of poor sleep habits.