Opera star Roberto Alagna, who stormed off stage after he was booed at Milan's La Scala, has claimed he was suffering from low blood sugar at the time.
Alagna claims his reputation has been damaged
Alagna, who walked out in the middle of Aida after being heckled, has said he plans to sue the opera house for dismissing him from the cast.
The singer, 43, claims if he gets emotional or stressed his system consumes sugars very quickly.
"I couldn't stay on my feet, I had to sit," he said.
His lawyer Marco Rocchini said his reputation had been harmed and he has a certificate from Alagna's physician confirming low blood sugar levels on the night.
"He is accused of abandoning the stage in a fit. The damage to his image is enormous," said Mr Rocchini.
A spokesman for the opera house said Alagna never mentioned feeling unwell after leaving the stage and had not provided management with any medical proof.
"If a singer is sick, he goes off stage, tells the musical director and a doctor verifies the condition, we inform the audience and the understudy goes on stage," said Carlo Maria Cella.
La Scala's management said they were not told Alagna was ill
The opera house has said it does not plan to sue Alagna for damaging the Aida production.
"What happened, happened. No-one wants to criminalise Roberto Alagna," Mr Cella added.
Alagna said the whole incident has left him exhausted and that he has not been able to sing at all since last Sunday.
"I've lost the desire. I've never gone more than two days without singing in my whole life," he said.
However on Thursday, the French-born tenor staged his own show outside La Scala.
Initially Alagna had blamed a hostile audience for his exit. The conductor said he had never seen a singer walk off stage mid-performance before.