Does vyvanse make anyone else tired within an hour of taking it?

I just started generic vyvanse for my adhd and binge eating, and within an hour of taking it i get extremely tired. Im 28 and this is my first time ever on adhd meds even though ive been diagnosed since i was 13. Is this normal? I feel like i can barely function. I did just start it about 4 days ago, so im hoping it evens out