How to remember if you've already taken your meds?

I don't think I took my vyvanse today.

Earlier today I was wondering, did I take my pill? I've got so much to do today! And I thought I had taken it, but wasn't sure. So I didn't take one at that point.

Now it's the afternoon, and I can tell I didn't take it, but it's too late now.

This happens to me a lot. Any suggestions?