A prisoner is thought to have gouged out his own eyes in a protest over how hot his cell had become.
The unnamed prisoner, a man in his 50s, has been taken to hospital after Monday's incident at HMP Nottingham.
The prisoner in question was reportedly just days away from being released.
But the Ministry of Justice would only say he was treated after an "act of self-harm".
A prisoner at HMP Nottingham was taken to hospital on Monday 21 July following an act of self-harm.
Staff reacted quickly and paramedics attended. No other prisoners were involved.
The prison is investigating the incident and police were informed as a matter of course.
Prison Service spokesman