I am prescribed adderall (dextroamphetamine and racemic amphetamine) and my doc had me take an oral fluid test but never explained why or what the results would show? why is a saliva test done?

Ask them!: Saliva tests could be used for many reasons. They could be checking hormone levels that may be affecting your condition. Also could be used to verify that you are taking the medicine (unfortuately adderal can be abused or sold and physicians have a legal requirement to take steps to prevent this).

For blood levels.: Saliva drug tests for Adderall (dextroamphetamine and racemic amphetamine) is usually done to see if you are taking the medicine and the drug level in your system. The usual cut-off point is 1, 000 ng/ml. Adderall (dextroamphetamine and racemic amphetamine) and other amphetamines stay in your blood for as long as 72 hours.