A "bad batch" of illicit pills has seen 12 people rushed to an Adelaide hospital, prompting a warning from doctors.

The average Saturday night sees one or two drug-related presentations at Royal Adelaide Hospital, emergency physician and clinical toxicologist Sam Alfred said.

But the emergency department had a "very unusual increase" over a 24-hour period.

"We had 12 people, who reported that they had taken recreational drugs in tablet form, present to the emergency department with significant toxicity as a consequence of their drug use," Dr Alfred said in a statement on Sunday.

The patients were found collapsed or unconscious before being taken to hospital on Saturday with agitation, nausea or vomiting, and exhibiting behavioural disturbances.

None of the 12 patients died and all have since been discharged but the spike has doctors concerned about an "increased risk" for drug takers.

"We are warning South Australians of the potential bad batch and remind them it is unsafe to take any type of recreational or illegal drugs," Dr Alfred said.

"Our concern as health practitioners is patient safety."

Dr Alfred urged anyone concerned after taking drugs to attend hospital straight away.

SA Health and SA Police have been notified of the spike.