Alec Reymond, her lawyer, said he had provided Geneva cantonal (state) justice authorities with a medical certificate justifying her absence from a planned meeting with an investigating magistrate in the Swiss city on Thursday.
Bhutto's doctor in the United Arab Emirates - where she lives in exile - has ordered her to avoid travel until June, said Reymond on Wednesday.
"The ailments from which she is suffering aren't detailed," Reymond said. "The doctor simply indicated that she is receiving treatment and cannot travel at present."
On Tuesday, Bhutto's husband Asif Ali Zardari turned down an offer from Pakistan's government for a temporary release from prison to answer questions in Switzerland, also on medical grounds.
Zardari is serving a seven-year sentence in Pakistan where he was found guilty in 1999 on several counts of corruption.
Zardari and Bhutto were convicted in July 2003 by a Geneva investigating magistrate on charges of laundering money through Swiss bank accounts while Bhutto was prime minister from 1993 to 1996. They were given six-month suspended sentences and ordered to return $11 million to the Pakistan government.
"The doctor simply indicated that she is receiving treatment and cannot travel at present"
lawyer for Benazir Bhutto,
The magistrate used a Swiss law which empowers high-level investigators to impose penalties without a court hearing. However, the law is normally invoked only when a defendant agrees to accept the punishment. Bhutto and Zardari contested the decision.
In November, a Geneva court overturned the penalty - a move which is automatic when defendants oppose a magistrate's ruling. The police court then passes such cases back to the cantonal (state) chief prosecutor.
The chief prosecutor decided to continue the inquiry, and another Geneva investigating magistrate ordered a new questioning, calling on Zardari, Bhutto and their former Swiss lawyer to appear.
Geneva justice authorities were not immediately available to say whether they would go ahead with Thursday's questioning without Bhutto and Zardari, but Reymond said doing so would be "a waste of time." He said he expected justice authorities to reschedule the meeting.
At Pakistan's request, Switzerland in 1997 froze the Geneva accounts of Bhutto, Zardari and Bhutto's mother, Nusrat Bhutto.
Swiss authorities said in 1998 they had found about 20 million Swiss francs - then worth $13.8 million - in accounts belonging to Bhutto and her family.
Investigators alleged that much of the money came from kickbacks from a Swiss company in exchange for a business contract.
Bhutto has twice been prime minister of Pakistan, but her governments were dismissed in 1990 and 1996 for alleged corruption.