"Have you been listening to a word of this?"
Most of the health tips given to patients during a consultation with their GP go in one ear - then straight out the other, says research.
However, the doctor who carried out the research says much of the blame lies with the medical profession for failing to get across the most important advice.
Patient representatives say that communication between doctor and patient needs to improve.
Dr Roy Kessels, from the University of Utrecht in the Netherlands found that between half and four-fifths all all medical information delivered during an average consultation was forgotten instantly by the patient.
In addition, half of the information that managed to gain a foothold in the memory of the patient was later recalled incorrectly.
The problem was particularly acute in older patients, he found, or in those who were anxious about bad news.
Dr Kessel's research was published in the Journal of the Royal Society of Medicine.
He told the BBC: "Doctors tend to give rather general guidelines rather than specific instructions.
"Instead of saying: 'You should give up smoking', they say: 'You should take better care of your health.'"
He said that while there was no direct evidence that this forgetting was harmful to health, it was likely that it would affect how well a patient stuck to their therapy or change in lifestyle.
He said that doctors did not tend to prioritise the most important information and give it at the beginning of the consultation, adding to the risk that it would be overlooked by the patient.
He called for greater use of visual aids to help patients remember facts about their condition.
Other research, he said had found that when information was given verbally, only 14% of it was remembered.
However, when pictographs were used, 80% of the information was absorbed by the patient.
Mike Stone, chairman of the Patients' Association, told BBC News Online that communication had to improve.
He said: "The problem is that you only have just under seven minutes on average - and a lot of patients just don't feel comfortable in the consulting-room environment.
"In that situation, a lot of patients just switch off."
A spokesman for the Doctor Patient Partnership told BBC News Online: "This is an unsurprising finding.
"Patients need simple, direct and easily digestible information about their medical problems.
"The GP appointment is commonly short and patients may well be understandably anxious about their condition.
"This situation is not conducive for communicating or retaining important messages about health."