The length of time it will take for Adderall to kick in can vary from user to user. Some will feel it kick in immediately, while others may feel it hours, weeks or even months later. It will depend on the exact dosage of Adderall being taken as well as other underlying issues or medications. Adderall is used to treat ADHD as well as narcolepsy. It is a combination of both the drugs amphetamine and dextroamphetamine and used as stimulants for the central nervous system.