NEW YORK (CBSNewYork) — More and more people are choosing urgent care over their primary doctor.

It’s a growing trend among millions of Americans that could be changing the health care industry, CBS2’s Dr. Max Gomez reported Tuesday.

Millennials are sometimes called “echo boomers” because many of them are children of us baby boomers. They’re still young and pretty healthy, so many don’t have a regular primary care doctor.

So when they get sick, they turn to quick and convenient urgent care clinics.

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

“I had a sore throat for the last few days and wanted to get checked out for strep throat,” Weiner said.

So he walked into Northwell Health-GoHealth Urgent Care in New York City.

“It was 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,” Dr. JD Zipkin said.

Zipkin said the centers treat a wide range of conditions — from cold and flu to broken bones and injuries that need stitches. But he said urgent care should not replace regular doctor visits and that real emergencies always require a trip to the ER.

“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,” Zipkin said.

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

In less than 30 minutes, Weiner left with a treatment plan for his sore throat.

Urgent care clinics can ease demand in crowded and expensive hospital emergency rooms. Plus, the clinics often refer complicated patients to the main hospital. Both are reasons many urgent care clinics are actually owned by major hospital systems.