As a young emergency room doctor recently graduated from Stony Brook University’s medical school, Dr. John D’Angelo faced undiagnosed ailments in vulnerable patients day after day. During the COVID-19 pandemic, he oversaw operations at Northwell Health facilities.

Beginning Wednesday, D’Angelo, 56, embarks on his latest challenge: CEO of Northwell Health, the state’s largest health care provider and private employer. The New Hyde Park-based system has 28 hospitals, more than 1,000 outpatient facilities and 104,000 employees in five states.

He takes over from Michael Dowling, Northwell’s high-profile CEO for more than 23 years, who oversaw an expansion of the health system and used his job to speak out against gun violence and advocate for public health programs. Dowling will become “CEO emeritus.”

D’Angelo has worked in a number of roles at Northwell since 2000. Northwell declined to disclose D’Angelo’s salary.

A self-proclaimed “tech geek,” D’Angelo spent his early years in the Bronx before moving to North Babylon at age 11. He and his wife, Dawn, have six children, ages 16 to 36, and live in Bayport.

Newsday spoke with him about Northwell’s future plans, why they’re expanding mental health services despite them losing money, and how the ever-rising cost of health care impacts Long Islanders. This interview was edited for space and clarity.

What did you learn during your early days in emergency medicine?

You have to be very good at navigating uncertainty. It’s that balancing act of leading with your gut or using the information you do have. The emergency department is the ultimate showcase of a team sport. It’s a real partnership with the nurses, the people at the desk … everything has to coordinate in a certain way.

Michael Dowling is staying on as CEO emeritus. How will you two work together?

Michael’s going to be focused on things he’s been very influential and passionate about on the public health stage nationally — gun violence and behavioral health. He’s always available to me as an adviser, which I’ll take full advantage of.

And what health topics are you passionate about?

I am a physician-CEO. I think that comes with some responsibility on what we’re here for and that’s to drive better health … I’m a little bit of a tech geek and I think about how we leverage data and technology to drive the future of care delivery.

The other piece is more of a personal journey. I took a much more proactive position on my own wellness about eight years ago. I dropped 60 pounds and changed my lifestyle. We have an epidemic of chronic disease. We have an aging population. We have all these dynamics that we are going to have to address.

Some critics have said health care consolidation leads to higher costs. Is there any response to that?

Not many hospitals are surviving that are independent anymore. That makes the argument that the consolidation and the economy of scales that come with it are a way for hospitals to survive, if not thrive, despite a very flawed financial structure for all stakeholders. I think we feel very strongly that our growth and our size and our scale and how we’ve been able to economize, especially a lot of the support structure — HR, IT — has really been part of our success.

What about future expansions?

We are growing more in Suffolk County. We’re growing aggressively in Queens and Westchester. A lot of independent medical groups and hospitals are going to continue to struggle, and they’re going to need somewhere to go.

Certain services we provide, we lose a ton of money, but it’s the right thing to do. Behavioral health is a great example. We keep expanding behavioral health services. We’re the second largest provider in New York State. It loses money, and the more we do, the more money we lose. When people focus just on “look at how much money you make here” — that helps offset the cost, so we can do the things that are part of our mission. Everything we make, we put back.

Is there any way to mitigate the increases in health care costs to consumers, to local governments and to businesses?

The cost of medical devices, technology — there’s great advancement that comes at great cost.

It’s why we are trying to also drive the for-profit side of the business, to drive alternative revenue streams, because what we get reimbursed for care, the cost of delivering the care, doesn’t cover the cost.

For example, GoHealth urgent care centers?

GoHealth. We have a pharmacy business that serves other hospitals and other direct-to-consumer things.

We have a very unorthodox Health and Human Services secretary, Robert F. Kennedy Jr., who is doing some things against the medical consensus. You also need to maintain good relationships with the federal government. How do you balance that?

If we’re going to focus on doing what’s best for the patient, we’re going to continue to recommend what is evidence-based medicine and what science has taught us. That’s certainly how we’re approaching vaccines.

RFK Jr. does have a bully pulpit. Is there a concern about someone having a bully pulpit who is not a doctor, is not a scientist?

Our direction to our doctors is you’re the person with that patient in front of you that’s responsible to give them the best advice possible. I like to believe patients trust their doctors. One of the privileges of being a doctor is you should be seen as someone who is not influenced by all the noise, that you’re influenced by what you know to be what the science shows.

Dowling had said cuts to federal scientific research funding could have disastrous consequences.

It would be a mistake to inhibit or impede the commitment to research in this country, and we do rely on funding from various sources. If one of those sources happens to go away, we are still committed to research. I do worry about the impact on continuing to drive innovation and deliver better care and figure out new ways to do so if the research engine in this country is slowed down or inhibited from doing what it’s been doing all along.