Perth Prison has been hit by a population crisis, placing a serious strain on lifeline services and extra pressure on staff.
The number of inmates at the 630-capacity jail has soared to 710, forcing more prisoners to share cells.
A total cap has now been set at 730, despite concern that some service providers will struggle to cope.
The increase has hit the healthcare team working to make improvements following a highly critical inspection report in October.
Perth and Kinross Health and Social Care Partnership said the population surge had become its biggest challenge.
Head of health Evelyn Devine said: “The healthcare workforce is designed for 630 prisoners, and we’ve been pushing the boundaries to 650 prisoners. Last week, the prison had 710 prisoners.
“We are worried all the good improvements that have been made could be lost very quickly.”