Several teenagers have lost consciousness after reportedly taking an unknown substance at a Gold Coast school on Wednesday.

A Queensland Ambulance Service spokesman said the students, from Saint Stephen’s College on Reserve Road, Upper Coomera, were suffering the effects of consuming the substance on Wednesday.

The students were understood to be falling in and out of consciousness.

Seven patients were taken to Gold Coast University Hospital in conditions that ranged from stable to serious but stable.

The QAS was called to the school about 12.50pm.

Saint Stephen's College is a co-education prep to year 12 independent school.

It was understood the college headmaster had been at a conference in Brisbane but would return to the school on Wednesday afternoon.

A Queensland Police spokesman said police were aware of an incident at the school and were investigating.