Hawaii Medical Service Association is proposing an average 49.1 percent rate hike — the highest its ever requested — for individual Obamacare plans in 2016.

The state’s largest health insurer said in a note posted on its website Monday that the rate will affect about 3 percent of its membership and is necessary to cover the “much higher than expected medical costs” for these members.

“At HMSA, we understand the frustration of rising health care costs,” said Michael Gold, HMSA president and chief executive offer, in the statement. “Our decision to ask for this premium increase was truly difficult.”

The insurer said it “explored every alternative for a smaller premium, but ultimately had to ask for this increase” for the following reasons:

>> Nearly everyone in Hawaii already has health insurance from their employer, Medicaid or Medicare. “The small number of people left without coverage often had serious health conditions. Many of these previously uninsured people purchased our ACA plans.”

>> ACA plans began in 2014 and are still new. “This is the first time we’ve been able to price these plans using actual claims and health information from these members. We’ve learned many of these members are using substantially more medical services and prescription drugs than we expected.”

>> Several thousand members from the Compact of Free Association (COFA), originally on Medicaid, purchased individual ACA health plans from HMSA this year.

Many of these members have conditions that will likely require “intensive medical services and expensive prescription drugs.”

“The ACA has helped thousands of Hawaii residents get health coverage. That’s good for the well-being of our state,” Gold said. “But it comes with a price that we’re seeing now.”

State Insurance Commissioner Gordon Ito, who regulates health plan rates, said the proposed increase for the ACA individual plan will be closely scrutinized.

“The Insurance Division will actively seek reductions to the proposed request, where possible, to ensure fairness to all parties involved,” Ito said. “If medical expenditures paid out for healthcare services under the ACA individual plan are too high, the division’s ability to drastically reduce this requested increase will be limited.”