Nationwide enrollment in health plans provided through the
That is down from 11.7 million sign-ups recorded in February when the 2015 enrollment period closed.
The tally still represents growth over 2014, when 6.3 million people were enrolled in health plans at the end of the year, according to updated 2014 figures also released Tuesday.
The new data also underscore how many consumers rely on federal insurance subsidies made available by the law. About 85% of 2015 enrollees are getting assistance to buy coverage on the marketplaces.
How long that assistance will remain available is unclear, however. The Supreme Court is expected to rule this month in a challenge that claims the law prohibits these subsidies in states that are not operating their own insurance marketplaces through the health law.
The health law allows Americans who don't get health benefits at work to shop among plans on state-based marketplaces operated by the federal government or by the states themselves, including California, Connecticut and Maryland.
Consumers making less than 4 times the federal poverty level – or about $97,000 for a family of four – qualify for subsidies.
Insurers must provide a basic set of benefits and cannot turn away consumers, even if they are sick.
Sustained growth in enrollment is considered key to reducing the number of uninsured and keeping premiums in check by getting healthier Americans into the market, key goals of the law.
"The health insurance marketplaces are working," Health and Human Services Secretary Sylvia M. Burwell said Tuesday.
Multiple surveys over the last year have recorded historic declines in the number of uninsured since the law's major coverage expansion began in 2014. Rand Corp., a Santa Monica nonprofit research firm, last month reported that the number of Americans without coverage declined by nearly 17 million.
But the coverage gains are jeopardized by the legal challenge before the Supreme Court, which may affect as many as 7.5 million consumers in 37 states.
There is also growing evidence that uncertainty over the case may also be pushing up insurance premiums, as insurers prepare for major disruptions that would be caused by the elimination of subsidies.