I want to drink 18 shake luxury meal replacement, it has ascorbic acid vitamin c 18 mg 30 % day value, i take the instant release adderall two times a day, will this protein 18 shake with vitamins especially c make my adderrall less effective?

Gastrointestinal : acidifying agents like ascorbic acid decrease the absorption, &, therefore, the blood level & clinical effect of Adderall, Adderall XR & Vyvanse (lisdexamfetamine). See www.drugs.com/cdi/adderall-xr-extended-release-capsules.html. Always tell your doctor before taking new medications, herbs, vitamins & supplements. Long-acting Adderall XR or Vyvanse (lisdexamfetamine) are easier to dose/ titrate & generally have less "rebound" effect.