"In fact, everything is normal," he told Moscow's Ekho Moskvy radio station from London. "It was just a strange thing when I suddenly felt ill, with high blood pressure and so on."
A medical exam showed no poisoning, he said. RIA Novosti reported the interview.
London's Daily Mail had reported that British police and radiation experts were investigating Berezovsky's "mystery illness." The paper said he flew to Israel for a checkup.
Berezovsky's friend, former KGB agent Alexander Litvinenko, died of radiation poisoning in London in 2006, and blamed then-Russian President Vladimir Putin for killing him.
In 2007, Britain asked Russia to extradite Andrei Lugovoi on suspicion of poisoning Litvinenko.
The Kremlin, which denies any role in the death, refused the request and wants Britain to extradite Berezovsky, whom it has accused for a decade of fraud and plotting a coup.
Notable deaths of 2014 [PHOTOS]
Syrian Al Qaida group executes Lebanese soldier