Talk to your doctor, but the simple answer is to take more. Vyvanse has a half life of about 12 hours, so if you take it in the morning then by evening the medicine is starting to heavily breakdown. It’s pretty common for people to take more at lunchtime to get them through the evening for that reason.

Two things:

1. Generally when you take medicine with high acidity food, like coffee, it will break down your medicine prematurely - you won’t get as strong as an effect. I had to stop taking my Vyvanse with orange juice because it basically nullified the medicine.

2. Talk to your doctor. I had chronic headaches that I found out were related to low blood pressure and dehydration. Drinking water instead of diuretics, like coffee, immensely helped me.