What happens if you take ADHD medication if you don't have adhd?

Lots. First of all, doing so is a federal offense. It's called drug diversion. So someone without adhd or a proper diagnosis should not be taking adderall (dextroamphetamine and racemic amphetamine). Tremors, irritability, rapid heart rate, increased blood pressure, arrythmia, headache, nausea, insomnia, anorexia & hallucinations are common effects of stimulants used without proper medical guidance. Little if anything good will result.