Paul has held a state-issued medical license since moving to Bowling Green in 1993. He received his first job from Dr. John Downing of Downing McPeak Vision Centers, which brought him to Bowling Green after completing his residency. Paul worked for Downing for about five years before parting ways. Afterwards, he went to work at the Graves-Gilbert Clinic, a private medical group in Bowling Green, for 10 years before creating his own practice in a converted one-story house across the street from Downing's office. After his election to the U.S. Senate, Paul merged his practice with Downing's medical practice. Paul has had two malpractice lawsuits filed against him since 1993. Paul was cleared in one case and the other was settled for $50,000. Regardless, his medical work has been praised by Downing and Paul has medical privileges at two Bowling Green hospitals. Paul specializes in cataract and glaucoma surgeries, LASIK procedures, and corneal transplants.
As a member of the Bowling Green Noon Lions Club, Paul founded the Southern Kentucky Lions Eye Clinic to help provide eye surgery and exams for those who cannot afford to pay. He is a regular presenter at the annual Men's Health and Safety Day conference held by The Medical Center of Bowling Green since 1998. In 1999 Paul founded the Non-profit organization National Board of Ophthalmology (NBO).