(Editor’s note: This story appears in full here. This excerpt is posted with permission from CNN.)

Dr. Michael Williams is Director of the UVA Center for Health Policy, a joint program of the Frank Batten School of Leadership and Public Policy and the University of Virginia School of Medicine, Department of Public Health Sciences.

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The plan for pharmacy company CVS Health to buy health insurance giant Aetna could not only set a record as the largest American health insurance deal in history, it could change the way you get health checkups or see a doctor when you’re sick.

…If Aetna customers’ pharmacy benefit provider and pharmacy services provider merge, it could be difficult for them to go outside their network for pharmacy benefits, and their pharmacy options could diminish, said Dr. Michael Williams, an Associate Professor of Surgery at the University of Virginia and Director of its Center for Health Policy, who is not involved in the merger.

“Certainly, if I was CVS and was in the end paying for Aetna’s services, I would limit as much as I can from which pharmacy you can get your medication,” said Williams, who is insured through Aetna and has treated Aetna-insured patients.

“The pricing will be one that is going to change for the patient,” he said. “The reality for the average consumer is that the number of choices that you’re going to have if you’re already insured with Aetna … will probably diminish.”

This aspect of the CVS-Aetna merger could impact prescription services as well as health services provided in CVS walk-in clinics. Overall, it seems to present a double-edged sword in the health care marketplace for consumers, Williams said.

“The other side of the sword, though, is that they will be able to dictate fees. They will tell you what medications they will cover, and your ability to therefore say ‘well, I need to get access to this kind of insulin or that kind of chemotherapy’ is going to diminish,” he said. “Your ability to seek other options will be constrained, so that’s a double-edged sword.”

…Health records from visits to clinics, pharmacies and doctors all could be more easily integrated into a patient’s file, Williams said.

…A pharmacy or Minute Clinic could be a first option of care for sick patients instead of a hectic emergency room. While Minute Clinics certainly have not replaced emergency rooms yet, some experts suspect that more clinics are expected to emerge and might aim to fill that role.

Having a more integrated system makes it easier for doctors to treat a patient as well as to monitor their health status and care, Williams said.

“If Aetna will maintain a health record of those encounters, now there’s a chance for that information to be part of a larger system view for each patient and groups of patients,” Williams said.

…”So there’s a potential upside for us if Aetna does this correctly.”

“Right now, if you go to Minute Clinic as one of my patients, unless you tell me, I have no way of knowing.”

…”I think that we’re going to see the growth of more and more clinics where health services are being provided in the CVS footprint geographically,” Williams said. “So if there isn’t a clinic already in your CVS, I think one is coming to a CVS near you in the near-term future.”