On an empty stomach, it takes about a half
hour to kick in and always lasts (for me) about 12 hours. You only need to take one. Vyvanse
has seriously changed my entire life. I am a much happier, less stressed, productive person. I have virtually no side effects except for a small decrease in appetite and mild to moderate when it wears off. I sleep like a baby, even though a side effect is insomnia. I'm so much more calm, neat, organized, motivated, punctual, and non-fidgety.