Two other officials said Sanha, who has been dogged by poor health since coming to power in 2009, was flown to Dakar on Wednesday and may have to travel to Cuba for further treatment.
“He is having some tests (in Dakar). After that we will see,” said the official, who asked not to be named.
The official did not say what was wrong with Sanha although he is known to have suffered from diabetes for years.
Concerns over the president’s health come as the tiny former Portuguese colony enjoys relative stability after years of turmoil, fuelled by the military’s meddling in politics.
International drug trafficking networks have also taken advantage of the weak government and corruption to turn the country into one of West Africa’s transit points for Latin American cocaine headed to Europe.
An official in Guinea-Bissau’s foreign ministry said Sanha may have to travel to Cuba for further treatment. Another diplomat said he had heard similar reports but was not able to confirm them.
Sanha reshuffled his government this week but the new cabinet has not been sworn in due to his health problems, officials in Bissau said.
Angola, also a former Portuguese colony, has dispatched a mission to try to help reform the fractious military, and squabbling between politicians appears to have eased for now.
But stability in the county, whose main legal export is cashew nuts, remains fragile and the planned retirement of soldiers and officers, some of whom are implicated in drug-trafficking, will test any progress made.