Disgraced US financier Bernard Madoff is being treated in a prison hospital for hypertension and dizziness, a US Bureau of Prisons spokeswoman has said, BBC reported.
Traci Billingsley denied earlier media reports that Madoff was assaulted at a prison in North Carolina.
Madoff, aged 71, is serving 150 years for a $65bn (£41bn) fraud.
He admitted defrauding thousands of investors through a Ponzi scheme, which pays out using new investors' money rather than from any profits.
He said the scheme had been running since the early 1990s.
It unravelled when Madoff's investors, hit by the economic downturn, tried to withdraw about $7bn, but he could not produce the money.
The list of his victims included film director Steven Spielberg's charitable foundation.