The 21st century health care system in the United States is not only complex, but also profoundly different from “what it used to be.” The changes are numerous and represent the major shifts involved in moving from a plan of protection and care delivery, based primarily on what the patient wanted, to a health system managed with skepticism. The American healthcare system has undergone drastic changes over generations and continues to evolve. Over the years, the medical field has always brought together society's best and brightest to help those in need. From treating cancer to childbirth to managing heart attacks, doctors have developed technologies and improved techniques. The three main changes revolutionizing the medical field are electronic medical records, demographic science, and clinical practice guidelines. With cutting-edge technology assessing patients on a large scale, doctors can learn the mortality rate, lifespan and disease frequency across the entire healthcare system. On an individual basis, the doctor can treat an illness. When looking at the population as a whole, problems such as cancer, heart disease and obesity constitute a growing epidemic. Population science can allow doctors to consider a large-scale way to cure these epidemics instead of just treating an individual. These epidemiological principles are now used in clinical studies to improve the evaluation of medical procedures. As the field of healthcare has evolved, new diseases and disorders have developed. It is impossible for a single doctor to know how to recognize and treat all the diseases in the world. With evidence-based guidelines, they can get closer. These guidelines may not have a perfect success rate, but they can make disease diagnosis easier. Healthcare professionals associated with medical billing and coding are familiar with the advancements technology has made so far. Over the past several decades, medical billing and coding has transitioned from a paper-based system to a computerized format. Under HIPAA laws, doctors have had to develop new software in order to send electronic bills. With the advent of electronic medical records (EMR), with the push of a button, doctors, nurse practitioners, and physician assistants can access every care a patient has ever received in every healthcare setting that patients have visited previously and can determine possible illnesses. . This also makes it possible to statistically document the population as a whole. The EMR can also make the healthcare system more transparent and enable integration of reimbursement data. As the healthcare system evolves, this will avoid unnecessary costs and make it easier to obtain the reimbursements needed to treat a patient..