People who are less assertive at the surgery miss out as "pushy patients" eat into their share of their doctor's time.
Doctors only have a handful of minutes per patient
A leading "health consumer" expert says that the problem is actually widening health inequalities, and making sure that less articulate - and more vulnerable patients - receive worse care.
Writing in the British Medical Journal, Hilda Bastian, managing editor of the Cochrane Collaboration Consumer website in Australia, says that a small number of patients are creating problems for health services.
Ministers say that they want to see "expert" patients in the NHS, but Ms Bastian describes this approach as "simplistic" and "risky".
The rise of web-based health information means that a group of literate and educated patients can arrive at the surgery with armfuls of print-outs about their condition, and long lists of questions for the doctor.
In the NHS, the average consultation time is less than 10 minutes, so doctors do not have much time to spare in a typical morning session.
Doctors are very very skilled in how to close down a consultation, so I'm not sure that these people are getting more than their fair share of a GP's time
Mike Stone, Patients' Association
"It worries me that this trend is deepening inequalities in healthcare, as the better-equipped patients corner more and more of their doctor's time," said Ms Bastian.
"Just how much more demanding can we get before we blow it for ourselves - not to mention take more than our fair share?"
However, Mike Stone, the chairman of the UK Patients' Association said that assertive patients were to be welcomed.
He said: "All patients should be assertive - many have to be this way just to get the treatments they deserve.
"Doctors are very very skilled in how to close down a consultation, so I'm not sure that these people are getting more than their fair share of a GP's time.
"In some circumstances, it is quite right that the GP should carry out a longer consultation - and in some cases a very short consultation is fine.
"What we want is good communication between doctors and patients."
He was backed by Judith Brodie, of the charity CancerBACUP, who said: "Surely it is every patient's right to be well informed about their own health and to ask questions of their doctor?
"This does not make a patient pushy, it simply means they are more able to be actively involved in their care - which should result in better care.
"The challenge is to make sure as many people as possible are in a position to do this "
Elsewhere in the British Medical Journal, a report gives tips on how to get the best out of a consultation.
It advises patients to make sure they understand fully what the doctor is saying - getting him or her to repeat it if necessary.
Other advice includes not being afraid to ask questions - and to be direct - even about the most embarrassing issues.