I started taking doxycycline 3 days ago, 100 mg. 2x/day for Lyme disease. I seem to be sleeping an awful lot, but the chief side effect is the nausea. This morning I vomited about 35 minutes after taking the pool. I'd eaten a little breakfast, but still felt incredibly nauseous. I just ate a large dinner and took the pill immediately after. I hope to keep it down.