Yes, taking Vyvanse before an amphetamine screening test can influence the result. The active ingredient in Vyvanse is converted to dextroamphetamine in the body, which is a type of amphetamine. Therefore, taking Vyvanse before the test can result in higher concentrations of dextroamphetamine in the blood, making it more likely for the test to detect it. It is important to consider the timing of medication when undergoing such tests.