The new GOP tax bill has the medical expense deduction — which largely benefits older Americans and those with a disability or chronic condition — squarely in its cross hairs.

Currently, individuals with large out-of-pocket medical expenses can report the figure as a tax deduction.

But if the tax bill passes, the medical expense deduction will come to an end after this year — part of what the proposal calls a “simplification and reform of deductions,” which also includes repealing other deductions.

To take the deduction, a person’s medical expenses, or those of their family, have to be very high, or more than 10% of adjusted gross income for non-seniors, and they must itemize those costs, which many people don’t do. Those expenses can include a wide range of medical fees and health insurance premiums.

Still, for a minority of people, the effect could be financially significant. More than nine million Americans itemized a total of nearly $90 billion in medical expenses on 2015 tax returns, according to the Internal Revenue Service.

Read: Here are the winners and losers of the tax plan, by income bracket

The Republican tax bill does increase the standard deduction significantly, approximately doubling it from the current level, which its authors said allows people to “immediately keep more of their paychecks — instead of having to rely on a myriad of provisions that many will never use and others may use only once in their lifetime.”

That means individuals that had been filing itemized deductions below the level of the proposed standard deductions ($12,000 for individual filers and $24,000 for joint filers) likely won’t be affected, tax experts said. Families with children will also likely benefit from a larger child tax credit, said Nirupama Rao, an assistant professor at the University of Michigan’s Ross School of Business.

But for those in the opposite scenario — whose total personal exemptions and itemized deductions exceed the proposed standard deductions — the change could potentially raise their tax bill, and it could also hurt people with a low-enough adjusted gross income that their medical expenses make up more than 10% of it, Rao said.

The deduction was intended for “expenses that one generally doesn’t have the option to not incur. If you are very sick or your kid is very sick you have to pay to treat and that expense makes you less able to contribute the pot of revenues that pays for government services,” Rao said. Not many people use it because it’s intended for very high expenses, she said, “but for those who use it, it can provide important relief.”

“Now, if your kid needs treatment that costs you $40,000, the government isn’t sharing that risk with you,” she said.

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Ending the deduction would save about $144.4 billion over the next decade, according to a Department of Treasury estimate, which ranks it among the items raising the most revenue in the tax bill.

See: Here are the most expensive elements of the new tax bill

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But trends in the wider U.S. health care system could also complicate eliminating the deduction.

Increasingly, more Americans — including those with employer-sponsored health insurance — are exposed to large out-of-pocket expenses under high-deductible health plans, especially through co-insurance. (Contributions to health savings accounts, which accompany high-deductible health plans, are separately tax-exempt, but they are typically under-utilized by individuals and their size is limited.)

In addition, Republican politicians have repeatedly tried to repeal the Affordable Care Act, and the Trump administration is also attempting to weaken the health law. ACA premiums have also been going up.

Those who are uninsured or under-insured, meaning their policies might just cover something like hospitalization rather than a wide range of offerings, might also have high medical expenses and thus need the deduction.

“That’s generally not happening right now — to the extent that people are insured they’re getting coverage for a broad range of things — but that’s another risk out there,” said Amy Bergner, managing director, health and benefits at PricewaterhouseCoopers.

See more: Obamacare helped make a 50% dent in personal bankruptcies

Prices of drugs for diseases like cancer and rare diseases are also on the rise, making out-of-pocket costs for those products rise, too.

Of course, the medical expense deduction change may not become part of the final bill, and the bill may not become law.

“While this provision helps offset the cost of increasing the standard deduction, we could see this deduction survive in some form as part of a final bill,” said Height Securities analyst Stefanie Miller. “The deduction is important to individuals who pay for health insurance premiums with post-tax dollars, especially the self-employed and early retirees facing high health insurance premium increases for 2018 in the unsubsidized individual insurance market.”

Somewhat ironically, Republicans pushed to lower the threshold for the medical expense deduction to 5.8% earlier this year as part of ACA repeal attempts, Miller noted.