Lohan, 26, had reportedly been shopping around rehab facilities that would let her continue to take Adderall, which she was prescribed for attention-deficit hyperactivity disorder.
Sources at TMZ said that Betty Ford's doctors are reevaluating Lohan's diagnosis -- and if she is determined not to have ADHD, she will be taken off the pill, which is known to be abused for its appetite-suppressing qualities.
The doctors will examine how effective Adderall is for Lohan should they confirm her diagnosis.
During her stay, the "Mean Girls" star will be on lockdown and will not be permitted to leave the premises, according to MSN.
2014: The Year in Music [PHOTOS]