The Hawaii Medical Serv-ice Association is proposing an average 43.3 percent rate hike for about 20,000 individuals in Obamacare health plans for 2017.

“I wish we didn’t have to ask for such a large increase, but we don’t have any other alternative,” due to a lack of healthy members in Affordable Care Act plans, said Michael Gold, HMSA president and chief executive officer, in a letter to members on the company’s website.

Many HMSA members in ACA plans have “serious health conditions that require costly medical care and prescription drugs,” he said.

“Many of these people couldn’t get health insurance before the ACA, and the federal law has helped them tremendously in getting access to doctors and hospitals,” Gold said. “Our challenge is that there aren’t enough healthy people with ACA individual plans. Healthy members keep premiums affordable and financially balance the members with serious illnesses. Without enough healthy members in these plans, we’re losing significant amounts of money.”

The state’s largest health insurer lost $17.5 million on Obamacare plans last year and anticipates a $15.5 million shortfall in 2016, he said.

“That’s $33 million lost in two years,” Gold added. “As a nonprofit, HMSA cannot afford to absorb these substantial losses. Doing that would require us to increase costs for other members, businesses and the community. Instead, we’ve asked for higher ACA individual plan premiums to make up for these financial shortfalls.”

HMSA, which has about 732,000 members, said it spent $1.20 on medical and prescription drug claims in 2015 for every $1 in premiums collected from ACA members, and $1.15 for every $1 in 2016. The losses are built into premiums for the following year.

The rate hike doesn’t affect HMSA members in employer-sponsored health plans, seniors in the Akamai Advantage plan or pre-ACA health policies known as grandmothered or grandfathered plans.

Meanwhile, Kaiser Permanente Hawaii is proposing to raise rates by 25.9 percent for nearly 14,000 ACA policyholders in an effort to “sustain and deliver high quality health care for all our members.”

Kaiser, which insures roughly 249,000 residents, blamed the significant increase on greater use of medical services by those previously uninsured, changes in programs and rules, and higher costs of prescription drugs, particularly newer specialty drugs.

“Even with these challenges, Kaiser Permanente will continue to offer coverage — including access to our complete network of world-class providers and services — through the health care exchange,” said Kaiser spokeswoman Laura Lott. “We continue to believe exchanges have great potential to improve access to care in the long term.”

A 40-year-old nonsmoker in the lowest-cost Obama-care plan currently pays $213.79 a month with HMSA and $236.24 with Kaiser. Those premiums would rise by $92.57 for HMSA and $61.19 for Kaiser. Under ACA plans residents can apply for tax credits, which could reduce the premiums.

HMSA proposed an average 49.1 percent rate hike — the highest it ever requested — for 2016 Obama-care plans, but the state reduced the increase to 27.3 percent. Kaiser proposed an 8.7 percent premium hike for this year but was granted a 34.4 percent increase by the Insurance Division.

Nationally, health insurers are struggling with how to balance the pool of newly insured — many of whom haven’t had medical care in years — with the population of healthier members in order to control premiums.

“Dozens of health insurers around the country are struggling with the same problem and have asked for major increases of up to 60 percent,” Gold said. “We’re doing everything we can to stabilize these premiums, but it’s much more difficult than we anticipated when these health plans began three years ago.”

The rate increases for policies under the Affordable Care Act, or Obama-care, would take effect Jan. 1. The state Insurance Division, which regulates health plan rates to ensure they are not excessive, inadequate or unfairly discriminatory, has an Aug. 23 deadline to approve the rates.

“Health care costs continue to rise beyond wages and inflation,” said Insurance Commissioner Gordon Ito. “This, combined with ensuring access to health insurance and health care for all, challenges health insurers.”