Pilots Unable to meet Requirements of a Medical Certificate

FAR 61.53 states that although a pilot may have a current medical FAA Medical certificate, if he or she has a medical condition that would make him or her unable to meet the requirements of the FAA medical certificate, or is taking medication or receiving other treatment for a medical condition that results in the person being unable to meet the requirements for the medical certificate, that pilot may not fly as pilot in command. 

 Likewise, if you're taking advantage of BasicMed, if you develop an adverse medical condition, you must either ground yourself or be treated by a physician before you continue to fly.