Ambulances have been called out to Perth Prison nearly 200 times in the last three years.
At least 60 visits have been made to Castle Huntly, Scotland’s only open prison.
Documents released under freedom of information legislation show only three other Scottish jails, all with larger populations, had more call-outs.
At least 55 of the calls to Perth Prison were classed as “immediately life threatening”.
Mid-Scotland and Fife MSP Murdo Fraser said the figures were “shocking but not particularly surprising”.
He said the call-out numbers added to HMP Perth’s reputation as one of Scotland’s “most violent jails”.
Mr Fraser said: “Prisons need to be absolutely secure and safe environments for both inmates and staff.
“It would unrealistic to expect there to be no incidents, but it’s extremely worrying to discover that ambulances are having to attend 999 calls on such a regular basis.
“Obviously, some of these ambulance call-outs will be for incidents unrelated to prisoner disorder and this should be recognised.
“However, a significant number will be a result of violence inside with a number considered life-threatening, so it’s clear that security needs to improve inside Scotland’s jails.
“Paramedics are under enough pressure without having to make these trips into Scotland’s prison estate.
“I hope the SNP government can offer more support to the Scottish Prison Service to ensure there are far fewer incidents to which ambulances have to respond in future.”
A Scottish Government spokeswoman said prisons are dealing with increasingly challenging populations.
“Up to 8000 people are in the care of the prison estate, with a range of complex health needs including substance misuse,” she added.
“While any one incident is one too many, we should never take for granted that Scotland’s prisons in general remain safe, stable and secure environments.”
No-one from the Scottish Prison Service was available to comment.
In October, it emerged that the cost of inmates trashing and setting fire to cells at HMP Perth amounted to more than £60,000 in the last four years.
Figures released by the Scottish Prison Service through freedom of information laws showed a cost of £59,159.82 from the 2015/16 financial year to 2017/18.
