Nuuanu resident Dwight O’Neill, a 71-year-old diabetic, pays about $90 a month for a vial of insulin. That same vial could cost him about $900 if his Medicare benefits change.

“If I don’t take it, I’m done in seven to 10 days,” he said. “It’s really about $900 a month for a vial of insulin to keep me alive.”

O’Neill was among the more than 175 seniors who attended a town hall meeting Friday hosted by advocacy group AARP, which launched a nationwide campaign to protect Medicare from any changes proposed in Congress that would increase costs and put benefits at risk for seniors and future retirees.

The group is lobbying to save parts of the federal Affordable Care Act that benefit seniors, including provisions that require insurance companies to cover people with pre-existing conditions and efforts to make prescription drugs more affordable. Republicans and President Donald Trump have vowed to repeal the ACA but have yet to reach an agreement on a replacement.

Under the ACA, insurers can charge older Americans three times more than younger people for the same policy. Congress is considering legislation to allow health plans to charge 50- to 64-year-olds as much as five times more for health coverage.

AARP also is trying to pre-empt congressional efforts to reintroduce a bill to change Medicare into a voucher system (also known as premium support), which would change Medicare from a guaranteed benefit and instead give seniors a fixed amount to purchase private insurance.

“These changes mean very hard times for a lot of people,” O’Neill said. “I was raised in a family that said America is the greatest place in the world and if you do the right thing, they’ll take care of you. I’m mad as hell at this.”

Democratic U.S. Rep. Colleen Hanabusa, who spoke at the meeting, urged seniors to voice their concerns and to lobby to keep Medicare intact.

“As we sit back and look at what is at stake with a repeal of the ACA and replacement … things that we have come to accept as part of the process for health care as we know it today is going to be absolutely affected,” she said. “The real unfortunate part is that I believe that we’ve all made promises along the way as to how we would be able to have all of us … retire with dignity without concerns about (money).”

Audrey Kubota, who also spoke at the AARP meeting at Harris United Methodist Church, is afraid of what the future holds.

The 73-year-old Ala Moana resident is battling a rare immune disorder and takes medication totaling more than $3,000 a month.

“Thanks to Medicare, I am not paying a penny,” she said. “This condition will not improve, so for the rest of my life I’m going to have to do weekly infusions. I don’t know how I’m going to find an insurance company that would take me (if Medicare is changed). It’s a heck of a lot of money if I have to put it out myself. I am concerned. I mean, my family lives a long time.”