Spokeswoman Traci Billingsley says Madoff is being treated at a hospital at the Butner federal prison in North Carolina. The 71-year-old disgraced financier was moved there Friday.
Lawyer Ira Sorkin says Madoff has "had some dizzy spells and some high blood pressure."
Billingsley said Thursday that Madoff was not assaulted at the prison.
Duke University Medical Center earlier said Madoff had been treated there. But spokeswoman Debbe Geiger says the hospital had never had a patient by that name.
Madoff has been imprisoned since March after pleading guilty to fraud and admitting cheating thousands of investors out of billions of dollars.