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The problem is, due to caffeine usage I often end up going to bed too early and wasting time trying to fall asleep.

Are there any methods to find out whether my body is ready to fall asleep?

I would really like to avoid wasting these big chunks of time between going to bed and actually falling asleep.

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Sorry for stating the obvious, but, first of all, if you think that caffeine has a strong and prolonged effect on you, why you are not limiting the consumption? Otherwise the usual advice is going to bed at the same time, do some physical exercise during the day, turn off the computer 1 h before going to bed... – laika Feb 11 '13 at 15:52
up vote 6 down vote accepted

The half life of caffeine is around 6 hours for an adult. So if you drink a cup of coffee at 3 PM, half of it will still be in your system if you try to fall asleep at 9 PM. Hence the recommendation to you is to stop drinking coffee well before afternoon.

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