The number of people enrolled in Medicaid and the Children's Health Insurance Program hit 10.1 million as of November, a 17.5 percent increase over the same time period last year.
Federal health officials announced the new figures Monday and touted them as evidence that the Affordable Care Act's Medicaid expansion is working in states that have adopted it.
"These numbers are encouraging — not because of the continued growth — but because they reflect the millions of lives changed by the Affordable Care Act," wrote Vikki Wachino, acting director of the Center for Medicaid and CHIP Services, in a blog post.
"The recently released enrollment report shows that Medicaid and CHIP enrollment rose in [expansion] states by nearly 25.5 percent in November compared to the July-September 2013 baseline period, while states that have not, to date, expanded Medicaid reported an increase of approximately 7 percent over the same period."
The Obama administration is working to encourage governors that have not accepted the Medicaid expansion to tailor the policy to their states in 2015.
Indiana became the latest state to expand Medicaid on Jan. 27 and will require that enrollees make small contributions to their health insurance premiums.