The big tax and spending package President Donald Trump signed into law on July 4, 2025, will cut government spending on health care by more than US$1 trillion over the next decade.

Because the final version of the legislation moved swiftly through the Senate and the House, estimates regarding the number of people likely to lose their health insurance coverage were incomplete when Congress approved it by razor-thin margins. Nearly 12 million Americans could lose their health insurance coverage by 2034 due to this legislation, according to the nonpartisan Congressional Budget Office.

However, the number of people losing their insurance by 2034 could be even higher, totaling more than 17 million. That’s largely because it’s likely that at least 5 million Americans who currently have Affordable Care Act marketplace health insurance will lose their coverage once subsidies that help fund those policies expire at the end of 2025. And very few Republicans have said they support renewing the subsidies.

In addition, regulations the Trump administration introduced earlier in the year will further increase the number of people losing their ACA marketplace coverage.

As a public health professor, I see these changes, which will be phased in over several years, as the first step in a reversal of the expansion of access to health care that began with the ACA’s passage in 2010. About 25.3 million Americans lacked insurance in 2023, down sharply from 46.5 million when President Barack Obama signed the ACA into law. All told, the changes in the works could eliminate three-quarters of the progress the U.S. has made in reducing the number of uninsured Americans following the Affordable Care Act.

The biggest number of people becoming uninsured will be Americans enrolled in Medicaid, which currently covers more than 78 million people.

An estimated 5 million will eventually lose Medicaid coverage due to new work requirements that will

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