Plain English Summary

A medication error is where a mistake in the use of medicines leads to inappropriate use of a medicine or patient harm.  This project reviewed published literature to understand the likelihood and implications of such errors.  We found 36 published research studies focussing on primary care, care homes and hospital care which reported error rates ranging from 0.2% to 90.6%. 

We found four studies relating to the UK which looked at the cost of medication errors in specific settings.  Those studies reported a wide range of estimates for costs from €67.93 per error for inhaler medication to €6,927,078 for legal claims associated with anaesthetic error.

From this published information, our research estimated that 237 million medication errors occur at some point in the medication process in England per year. This is a large number, but 72% have little/no potential for harm. It is likely that many errors are picked up before they reach the patient, but we do not know how many.  We estimated that 66 million errors which could affect patients’ health occur per year, 71.0% of these in primary care which is where most medicines in the NHS are prescribed and dispensed.

There is little evidence about how medication errors lead to patient harm. From the limited information available, we estimated NHS costs of avoidable side effects from drugs at £98.5 million per year, consuming 181,626 days in hospital, causing 712 deaths, and contributing to 1,708 deaths.  These estimates are based on studies at least 10 years old, so may not reflect current types of patients or the ways doctors and other clinicians now work.  This may be an underestimate as only short-term costs and effects on patients’ health were included, and we had no data relating to care homes.