A source confirmed to PEOPLE that the 51-year-old Dance Moms star was admitted to hospital for a thyroid condition.
Miller was taken to an emergency room in Los Angeles, according to TMZ, which first reported the news.
The Dance Moms star had been serving her 366-day sentence for bankruptcy fraud at the Victorville Federal Correctional Institution in California since July.
She was transferred at the end of March to the Residential Reentry Center in Long Beach, a facility that provides a structured and supervised environment where she’ll be given employment counseling, job placement and financial management assistance.
She’s scheduled to be released May 25, TMZ reports.