New research shows one-quarter of those surveyed have deliberately not followed instructions about treatment prescribed by a doctor, while only one-fifth always complete a course of medication.
The study, by Pharmacy Voice, shows many patients do not believe there is anything wrong with not following instructions, with one-quarter believing that a course of treatment does not need to be followed rigidly to get better.
Nearly half of those surveyed (45 per cent) said they trusted their body telling them they felt better more than a prescription course of a treatment. However, experts say that while symptoms can abate, this does not always mean the patient has recovered.
There is particular concern over people not finishing courses of antibiotics, which can make bugs resistant, presenting danger not only to the patient but also to others.
One in ten of those polled admit to taking more than the recommended dosage, while one quarter do not always use measures when taking liquid medication. One in seven say they have used out-of-date medicines and one in 20 even use medication prescribed to family or friends.
More than 40 per cent admit to keeping unused prescribed medicines in reserve, while fewer than 40 per cent following recommendations to return unused medicine to the pharmacy, with one quarter throwing unused medication in the bin or in the toilet.