Many patients are being prescribed unnecessary and even harmful treatments, a report warns.
The review, in England, suggests one-tenth of items dispensed by primary care are inappropriate or could be changed.
Around 15% of people take five or more medicines a day - some are to deal with the side-effects of the others.
The government is appointing a prescribing tsar to help with the issue and stop waste.
Too much medicine
The more medicines a person takes, the higher the chance that one or more of them will have an unwanted or harmful effect.
Overprescribing can happen when:
- a better alternative is available but not given
- the medicine is appropriate for a condition but not the individual patient
- a condition changes and the medicine is no longer appropriate
- the patient no longer needs the medicine but continues to be prescribed it
Chief pharmaceutical officer for England, Dr Keith Ridge, said: "Medicines do people a lot of good and this report is absolutely not about taking treatment or services away from people where they are effective. But medicines can also cause harm and can be wasted."
The number of items dispensed by GPs and other primary care providers has doubled in recent years, from an average of 10 per person in 1996 to around 20 per person now, according to the report.
Repeat prescriptions make up around three-quarters of all prescription items.
And around 6.5% of hospital admissions are caused by adverse effects of medicines. This rises to up to 20% in the over-65 age group.
Improved patient records and handovers between hospitals and GP surgeries are among the recommendations made in the report.
Clinical pharmacists working with GPs to review medication and a move to more personalised care is already helping, say experts.
Prof Martin Marshall, who chairs the Royal College of GPs, said: "Prescribing is a core skill for GPs and many of our nurse and pharmacist colleagues in primary care and doing whatever we can to prescribe the most appropriate medicine for our patients, in an evidence-based way is something we strive to do on a daily basis - and in the vast majority of cases, this review shows this is happening.
"With our growing and ageing population, with more patients living with multiple, chronic conditions, many people are taking several medications in order to manage their various health illnesses, and the interaction between various medicines is something prescribers will take into account.
"In most cases, these medicines are necessary, appropriate and of benefit for the patient - but the aspiration to reduce the number of medications a patient is taking, where safe and possible, is a good one.
"GPs will only ever prescribe medication to patients in conversation with them,and after a frank discussion about the risks and benefits of the treatment - and when alternative options have been explored.
"What GPs and other members of the practice team often need, however, is better access for their patients to alternative, non-pharmacological treatments, which can be patchy across the country."