Uber is driving deeper into health care by offering to take patients in every U.S. market where it operates to their next medical appointment.

The ride-hailing service said Thursday its Uber Health business will handle rides set up by doctor’s offices or other health care providers and then bill that business, not the patient, for the service. The company said rides can be set up within a few hours or days in advance. Patients won’t need access to a smartphone to use the service.

Uber began testing the service last summer. More than 100 health care providers have signed up, including hospitals, clinics and physical therapy centers.

Company leaders said they are expanding because there’s a need. They cite federal government research that estimates that more than 3 million people do not obtain medical care because of transportation problems.

“There are a lot of people out there who are not going to the doctor simply because they can’t physically make it there,” Uber Health executive Jay Holley said.

He added that the service also represents a business opportunity for Uber by connecting the company with a lot of first-time users.

Uber will bill care providers who sign up for the service monthly based on their usage. Holley said some may pass the cost on to their customers, but most of the providers it has worked with so far pay for the rides out of their operating budget.

Uber rival Lyft offers a similar service called Concierge, which allows health care providers to set up rides for patients to get to appointments. The providers pay for the rides. Lyft also has patient transport partnerships with larger health care providers.

Health insurers and others have long recognized the need to help some patients, especially those with low incomes, make their medical appointments.

Molina Healthcare Inc. has offered a transportation benefit to its customers for around 25 years and says that more than 3 million people are eligible.