Ramadan's lawyers had pushed for his release since he was detained on 2nd of February, arguing his multiple sclerosis and nerve damage could not be adequately treated behind bars.
The Britain's Oxford University professor denies charges that he raped two women in France.
A court-ordered medical examination last Thursday found that the 55-year-old Swiss academic's condition was compatible with detention.
The day after the test, he was hospitalised for four days due to what his entourage said was a worsening of his condition.
Ramadan has complained that the medical tests were only cursory and that the doctor examining him did not have access to his medical records.
He refused to appear at Thursday's hearing at the main Paris appeals court.
Ramadan's two accusers went to the police in late October, both alleging that he had raped them in French hotel rooms.
French authorities ordered Ramadan to be placed in custody after he was charged, judging him a flight risk.
His lawyers have unsuccessfully proposed handing over his Swiss passport, bail of €50,000 and daily check-ins at the police station to secure his release.
His supporters -- including two million Facebook followers -- have lashed out angrily at his arrest, with many complaining that he has been unfairly targeted because he is Muslim.
Henda Ayari, one of the two women who made a complaint, was placed under police protection in November after receiving death threats.
- with AFP