This is a very important consideration. First off, all participants in the DISCO study will be under the direct care of a physician, who will monitor their progress, review all laboratory investigations, help manage side effects, and refer to other health care providers if necessary. No medication is entirely, 100% risk-free, and even very safe medications like doxycycline need to be considered using a ‘pros and cons’ approach. Doxycycline has been used for decades, with many people using it long-term, so as a medical community we have a lot of experience using it. There have also been many studies on doxycycline published over the years. This collective knowledge accumulated over decades means that we have lots of reliable and specific information on how people tolerate it, and how safe it is. Like most antibiotics, doxycycline may cause some gastrointestinal (GI) upset, like reflux (heartburn or indigestion), nausea, vomiting, or diarrhea. Though these are rare (all occur in less than 5% of people taking doxycycline), they do occur, and usually will resolve on their own. Taking this medication with food and water can also help prevent these side effects. Doxycycline can also rarely result in a skin rash, and makes some people more sensitive to the sun, so wearing sunscreen and using other sun-protection measures is important.