I have been taking Doxycycline Hyclate 100mg twice a day for over two years now. It was a rough road in the beginning. If I don't take it with a good amount of food, I get indigestion, followed by urgent bowel movement, then nausea leading to vomiting. Every time, within half an hour of taking it. If I take it with yogurt or fruit, same thing happens, so I eat more substantial or starchy foods. The difference in my acne is miraculous, so I keep taking it. All my side effects are temporary, no lasting effects. The warning on the label about avoiding sun is there for a reason, I burn so easily now, even while riding in the car on a sunny day, and it feels like tiny droplets of hot oil being spattered on my skin.