I take adderall (dextroamphetamine and racemic amphetamine) xr an i wake up with it still in my system why?

This depends: This depends on what time you take the Adderall (dextroamphetamine and racemic amphetamine) xr. Duration of effect is generally 10-12 hours. People usually take it in the morning in order to have focus in the day and be able to sleep at night. There may still be some in your system at night but not enough to disturb your sleep. If you are having sleep difficulty though, please tell your doctor.

Based on half-life: The half-life of the drug can range from 10 to 15 hours, which means that half the amount of the drug in your system is metabolized and leaves every 10-15hrs. In a 24hr period, there will still be small amounts in your system. If you take it daily, there will always be some in your system and can take a couple of days to fully leave. The key is to not have high levels at night so you can sleep.