Patients are wasting prescription medicines by not completing the course of treatment, doctors believe.
Some GPs thought patients should be penalised
Two fifths of 1,000 GPs polled thought their patients were wasting prescription medicine with young and old people the worst culprits.
A quarter said non-compliance was most likely when patients believed they were better before finishing a prescription, Norwich Union Healthcare reported.
But patients said they were not being given enough advice by doctors.
One GP blamed the statistics on moves by patients to take more healthcare decisions into their "own hands".
Dr Ann Robinson said: "One of the reasons for this wastage is that many patients now prefer to take their health into their own hands and decide when and how to use the drugs they have been prescribed.
"What's more, tough targets mean less time with patients and less focus on educating them about what's best for their wellbeing.
"I believe that these days much of the waste also occurs because the doctor has not spent enough time with the patient and hasn't fully understood their needs and concerns."
The report found that 65% of GPs are concerned that they lack time to give patients the care they need.
Doctors estimated that 36% of patients now self-diagnose ahead of appointments.
One in five even said patients should be financially penalised for not completing a treatment.
Dr Doug Wright, clinical spokesperson for Norwich Union Healthcare, said: "Most GPs agree that improved patient education is the way forward in terms of dealing with this problem.
"And while these findings highlight the fact that GPs have a responsibility towards the patient, the reverse is also true and patients need to take responsibility for completing the treatment prescribed by their doctor.
A spokeswoman for the Patients Association said: "This is caused by doctors not properly explaining to patients what they should be doing.
"There is so much red-tape these days, GPs just do not have the time."
A Department of Health spokesman said: "We fully agree that wastage needs to be reduced as much as possible."