Whenever i take my adhd meds i have a feeling of anxiety and my heart beats fast. why?

Stimulant SE: Stimulants activate the fight-or-flight system, elevating both hr & bp. Either that or some other effect can cause some people to feel anxious. Usually dose related & sometimes gets better with time, but the anxiety can be bad enough to merit switching to a different med class. Sometimes one stimulant class will do it and not the other; nonstimulant adhd meds much less likely to cause anxiety.

Stimulant effect: Please let the prescribing doctor know this is happening. It could be from the medication, or from using caffeine or chocolate with the medication. Or from a comorbid disorder like anxiety disorder. Or from using other medications such as decongestants. If none of these are present, then you may need a dose adjustment or change.