You should know how long does modafinil last in your body. This would allow you to properly time your daily schedule and be able to sleep at the right time. Modafinil is a racetam mixture of two enantiomers: S-enantiomer and R-enantiomer.
S-enantiomer is short acting and has a half life of only 14 hours. R-enantiomer is slower and takes longer to reach peak blood-plasma concentration level. Roughly speaking, it has a half life of about 15 hours.
So for an average person, it would take about 15 hours to be able to fall asleep after Modafinil kicks in. Modafinil takes anywhere between 30 minutes to 2-3 hours to be absorbed into the bloodstream.
So How Long Does Modafinil Last?
If you are like me and prefer to be asleep before midnight, you need to make sure you take the pill at the right time. We know about the 15 hours half-life. Let us add two hours for it to get into our system. This gives us a 17 hours window.
What this means is, you need to take your modafinil pill at 7AM in the morning if you wish to sleep by 12AM (midnight). Obviously this approximation might vary from person to person depending on your body and how well your respond to modafinil, but this is still an accurate average figure.
With experience you will be able to better determine the best time to ingest modafinil according to your body.