Hawaii's doctor shortage is getting worse, and it's getting especially difficult to find a physician on its neighboring islands.

The state is nearly 900 doctors short of the amount it should have based on population, according to the University of Hawaii John A Burns School of Medicine's Area Health Education Center. The shortage is expected to jump as high as 1,500 by 2020, school researchers said.

The center is trying to find ways to deal with the issues that make practicing medicine in Hawaii difficult, including government regulations and the state's high cost of living.

The shortage is up nearly 20 percent from 742 in 2013, and 43 percent from 622 in 2012, the Honolulu Star-Advertiser reported last week.

"I would already call it a crisis," said Kelly Withy, primary researcher for the center's Physician Workforce Assessment. "You don't realize how desperate it is until you can't find the care you need."

Many patients wait months to get an appointment. In many cases — especially on the neighboring islands — people aren't getting prompt treatment for serious diseases such as cancer, she said. On the Big Island, it can be two to three times more difficult to find a primary care physician, the type of doctor the state needs the most.

One-third of Hawaii's doctors will reach retirement age in the next five years.

Despite the shortage, there are fewer than 40 positions for doctors in the community, Withy said.

"Traditionally, physicians chose to open their own practices, and nowadays they don't want to," she said. "They want a job. So even if we had 800 doctors who wanted to move to Hawaii, unless they wanted to open their own practice, we could not accommodate them."