McCready, 28, was found unconscious Friday in a hotel lobby, according to authorities in Pinellas County, Fla. An incident report did not list the nature of the overdose.
Last week, McCready was charged in Arizona with identity theft and other counts. Within the past two years, she has also faced allegations of driving under the influence and a drug violation.
Dennis Tomlin, who had been her attorney until midday Monday, declined comment on the singer's situation Monday night except to say the singer has retained another lawyer.
Tomlin said earlier Monday that McCready had gone to Florida "to visit her mother when she found out about the potential charges in Arizona. The stress got to her and she ended up in the hospital."
He said then that she was in intensive care.
Details concerning the charges filed last week in Mohave County, Ariz., were not immediately available. Besides identity theft, charges against McCready included attempted fraudulent scheme and artifices, unlawful imprisonment and hindering prosecution.
Tomlin said last week that the singer was helping Arizona authorities apprehend a con artist who had bilked her and other celebrities out of large sums of money.
He did not elaborate on the details and declined to discuss them Monday night.
In May, McCready was charged in Tennessee with driving under the influence and driving with a suspended license.
Last year, she pleaded guilty to fraudulently obtaining the painkiller OxyContin at a pharmacy. She was fined $4,000, sentenced to three years of probation and ordered to perform 200 hours of community service.
She was scheduled to be in a Williamson County court Monday for a probation violation hearing. A judge ordered Tomlin to produce an affidavit from her doctor by Wednesday.
McCready had a No. 1 hit in 1996, "Guys Do It All the Time."