Police are investigating the incident, in which the man is thought to have taken multiple ecstasy tablets after being confronted by staff at the city centre venue.
A Police Scotland spokesperson said: “Around 11.55pm on Saturday March 29, police were called to a report of a man taken ill after taking illegal drugs while being searched in the queue for the Arches nightclub.
“The 39-year-old was taken by ambulance to Glasgow Royal Infirmary where he is in a serious but stable condition.”
17-year-old Regane MacColl died after visiting the venue in February. She is thought to have taken a ‘Mortal Kombat’ ecstasy pill, which have been linked to a number of serious incidents in recent months.
The Arches has since introduced a number of safety measures at police request, including increased checks for illegal drugs, and raising the minimum age for club nights to 2.