NEW YORK (CBSNewYork) – What did you do the last time you had a sore throat, a bad cold or a fever?

Chances are you didn’t make a doctor’s appointment. Instead, millions of Americans are going to urgent care centers.

CBS2’s Dr. Max Gomez takes a look at how those centers are changing the healthcare industry.

David Weiner knew it was time to see a doctor after a feeling under the weather for almost a week.

“I had a sore throat for the past few days and wanted to get checked out, and a rash on my hands and face,” Weiner said.

Weiner walked into Northwell Health-GoHealth Urgent Care in New York.

“You are seen quickly and get good service, and much easier than going to my primary care doctor,” Weiner said.

New research in JAMA Internal Medicine finds the number of people treated at urgent care centers has more than doubled over the past eight years, while visits to primary care doctors and the emergency room for non-life threatening conditions are declining.

“We are a lot more convenient. Patients can look at our wait times live online,” said Dr. J.D. Zipkin of Northwell Health-GoHealth Urgent Care.

Dr. Zipkin says the centers treat a wide range of conditions: From cold and flu to broken bones and injuries that need stitches. He says, however, urgent care should not replace regular doctor visits and that real emergencies always require a trip to the emergency room.

“The time that is not appropriate to go to urgent care is things that really need the emergency room like heart attack, strokes, major motor vehicle accidents or any other large trauma that really needs an emergency room,” Dr. Zipkin said.

Most urgent care visits cost significantly less than an ER visit, are similar in cost to a primary care visit and are usually covered by insurance, Gomez reported.

In less than 30 minutes, Weiner left with a treatment plan for his sore throat. The rash was poison ivy.

Urgent care clinics can ease demand in crowded and expensive hospital ERs, plus the clinics often refer complicated patients to a main hospital. Those are both reasons many urgent care clinics are actually owned by major hospital systems.