The majority of doctors admit that they have prescribed a patient a placebo.
Ninety-seven per cent have handed out dummy treatments to patients at least once in their careers, a poll of 783 UK doctors found.
About one in eight said that they had given out "pure placebos" such as sugar pills and saline solutions, according to the survey published in the journal Plos One.
And 97% said they had prescribed "impure placebos" such as antibiotics for suspected viral infections or non-essential physical examinations and blood tests to reassure patients, said the researchers from the universities of Oxford and Southampton.
Doctors said they handed out the dummy pills for reassurance or to induce psychological effects of treatment.
"This is not about doctors deceiving patients," said Dr Jeremy Howick, co-lead author of the study from the University of Oxford.
"The study shows that placebo use is widespread in the UK, and doctors clearly believe that placebos can help patients."
Professor George Lewith, co-lead author of the study from the University of Southampton, said: "Other previous published studies by Southampton have clearly shown placebos can help many people and can be effective for a long time after administration.
"The placebo effect works by releasing our body's own natural painkillers into our nervous system.
"In my opinion, the stigma attached to placebo use is irrational, and further investigation is needed to develop ethical, cost-effective placebos."