underactive thyroid
"I've been taking levothyroxine for about 30 days now and feel less lethargic and cranky. However, the pill causes my stomach to produce lots of acid in the morning, which makes waiting to eat breakfast an issue.  I have always had an iron stomach that can handle anything without getting upset, including medication when empty, so I'm not excited about this new problem. I have also noticed that my energy level sometimes fluxuates significantly a couple times a day. Improvments still needed."