Ambulances responded to 999 calls at Scotland’s jails more than 500 times last year.
The figure of 536 is down from 2017, when paramedics attended 803 emergency call-outs at prisons and youth detention centres.
Barlinnie prison in Glasgow received the most emergency responses, with 115 incidents.
The figures were obtained by the Scottish Conservatives following a freedom of information request in October and do not include call-outs towards the end of the year.
Of the 999 calls recorded in 2018, the Scottish Ambulance Service said 134 were dealt with as “immediate life-threatening” situations.
The Tories raised concern at the number of emergency call-outs and said security needs to be improved at Scotland’s jails.
Justice spokesman Liam Kerr said: “It would be 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.
“Many of these are considered life-threatening matters, so it’s clear security needs to improve inside Scotland’s jails.
“Paramedics are under enough pressure without having to make these trips into Scotland’s prison estate.”
The Scottish Prison Service (SPS) said it had its own medical staff on premises to deal with all but the most serious needs.
A spokesman said: “We will contact the blue light services if requested for medical purposes or other reasons.”
The SPS reported 25 deaths in custody in 2018.