Ambulances were called out to the headquarters of one of Europe's largest sports retailers 76 times in two years, a BBC investigation found.
Many of the calls, for workers at Sports Direct's complex at Shirebrook, in Derbyshire, were for "life-threatening" illnesses.
Former workers said some staff were "too scared" to take sick leave because they feared losing their jobs.
Sports Direct said it aimed to provide safe working conditions for all.
'Working under fear'
A total of 76 ambulances or paramedic cars were dispatched to the distribution centre's post code between January 2013 and December 2014, with 36 cases classed as "life-threatening", including chest pains, breathing problems, convulsions and strokes.
A further seven calls for ambulances were made but cancelled.
The figures, which came from a Freedom of Information request made by the BBC's Inside Out team to East Midlands Ambulance Service, also revealed the service received three calls about women having pregnancy difficulties, including one who gave birth in toilets at the site.
The details have since been passed to the Health and Safety Executive which has said it will examine the data.
Of the 999 calls, six were about car accidents on a road or car park next to the centre, one was for a dog bite and at least two were for a store on the site.
It is not clear exactly how many of these calls were for the thousands of agency workers on site.
One of the cases involved 52-year-old Guntars Zarins, who suffered a stroke in the warehouse canteen.
His daughter Liga Zarina-Shaw said Mr Zarins had gone to work with flu symptoms because he was too frightened to take time off.
The family does not blame Sports Direct or the agency which employed him for his stroke but Ms Zarina-Shaw said her father was worried about his job.
"He [was] even scared to take one day sick," she said.
"Now I know why, because what is happening there is not normal," she added.
Mr Zarins was paralysed down his right side but has since had another stroke and has returned to hospital.
Ms Zarina-Shaw said workers were worried about a "six strikes" policy used by an agency that supplies staff to Sports Direct.
A document produced by one of the agencies states: "Any person who exceeds six strikes within a rolling six-month period will have their assignment at Sports Direct ended."
Recruitment agency's six-strike policy
Workers can receive a strike for a range of "offences" including:
- Period of reported sickness
- Excessive chatting
- Excessive or long toilet breaks
- Using a mobile phone in the warehouse
The document adds agencies can end an assignment "at any time without reason, notice or liability".
Unite said it had been told that last year there were about 3,000 agency workers at the Shirebrook headquarters of Sports Direct, which was founded by billionaire Mike Ashley.
Sports Direct has also reported accidents in its warehouse have doubled in the past financial year.
The firm put the rise in accidents down to on-site building work, which has resulted in "increased footfall and decreased workspace".
According to council figures, there were 38 accidents reported across 2013 and 2014, including a fractured neck, when somebody was struck by a moving object, a crushed hand from moving machinery and back and head injuries.
At the firm's annual meeting, Keith Hellawell, the chairman, told shareholders he was satisfied the company complied with health and safety regulations and any concerns were investigated immediately.
The firm has previously been criticised as "Dickensian" in its employment practices.
In a statement, Sports Direct said: "Sports Direct aims to provide working conditions in compliance with applicable employment and health and safety legislation and seeks to provide safe working conditions for all staff working in our warehouse."
Adding: "We have a good working relationship with our local environmental health officer and we work together to maintain and improve the safety of our working conditions."
The firm added that only 24 ambulances were called directly to its warehouse during the period covered by the Freedom of Information request.
The BBC was also told it was incorrect to suggest workers went to work poorly because of the strike system and that agency staff should not fear losing their jobs if they called in sick.
Inside Out is broadcast on BBC One East Midlands at 19:30 on Monday 5 October and nationwide for 30 days thereafter on the iPlayer.