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Why half of all medicines are taken incorrectly

11 min read
Ruhige, warm beleuchtete Wohnszene mit einer offenen Holz-Pillendose, umgeben von bunten Tabletten in einzelnen Fächern, und einem Wasserglas auf einem Holztisch am Morgen

It usually starts harmlessly: one tablet in the morning, one in the evening, then a third is added because blood pressure is no longer the only issue. After a few years there are three or four different packs on the kitchen counter, and at some point you lose track of whether today's midday tablet has already been taken or not. This everyday picture is behind one of the most robust figures in health research: on average, people with a chronic condition take their prescribed medicines as intended only about half the time. In other words, medicines are surprisingly often taken incorrectly: too late, in the wrong dose or not at all. This is not a side note, but an assessment the World Health Organization has confirmed for more than two decades.

Researchers call this gap between prescription and actual intake medication adherence, and it is much more complicated than "forgetfulness" suggests. It has to do with memory, but also with routines, with the design of packaging and with the simple question of how well a medication schedule fits into daily life at all. Anyone who wants to understand why so many people, regardless of education, income or good intentions, struggle with this task needs to take a closer look at the numbers, where they come from and their limits.

What "adherence" actually means

Until the 1970s, medicine spoke of "compliance", roughly meaning obedience. The term described a clear division of roles: the doctor prescribes, the patient follows. Critics increasingly found this patronising, because it reduced people to the role of order-takers. In the late 1990s, the term "concordance" was proposed as an alternative, meant to emphasise a shared decision between clinicians and patients. In practice, however, this approach was hard to prove and never really caught on.

Today the term "adherence" has become established in the literature. It describes how consistently someone sticks with a therapy once started, without assuming from the outset whose "fault" a deviation is. This change in terms is more than semantics: it reflects the insight that not taking medicines is rarely about lack of will, but about a combination of memory, daily organisation, side effects, costs and, often underestimated, the simple practicality of a medication schedule.

The figure the WHO has cited for more than 20 years

In 2003, the World Health Organization (WHO) published the report "Adherence to Long-term Therapies: Evidence for Action". Its central statement, cited in countless studies since: in developed countries, adherence to long-term therapies for chronic conditions averages only about 50 percent. In developing countries, according to the WHO, the rate is even lower. For one condition, high blood pressure, the report gave example figures: 27 percent in the Gambia, 43 percent in China and 51 percent in the USA.

The WHO drew a conclusion from this that is still quoted today: improving adherence could have a greater effect on the health of populations than any improvement in specific medical treatments. That may be surprising at first, but it makes sense if you consider that even the most effective medicine does nothing if it isn't taken. An important caveat: the 50 percent figure is a rough average across very different conditions, countries and measuring methods. Depending on the study, diagnosis and method, actual values vary considerably, from under 30 to over 90 percent.

Why medicines are taken incorrectly, and not out of carelessness

Researchers roughly distinguish between two kinds of non-adherence. Unintentional non-adherence happens when someone simply forgets a dose, sleeps through it, is away from home or their daily structure gets disrupted: a missed train, a hospital stay, a move, and the usual routine falls out of step. Intentional non-adherence has other reasons: side effects, doubts about whether the medicine is needed, costs, or the feeling that taking it is a reminder of one's own illness.

The unintentional kind in particular is closely linked to how daily life is organised. Anyone who has to take several medicines at different times needs not only a good memory, but also a system that supports remembering and keeping track. This is exactly where one branch of research comes in, which looks not at active ingredients but at how intake is organised: through packaging, through aids, through routines.

The more complicated the schedule, the bigger the gap

A frequently cited review by Karen Ingersoll and Jessye Cohen from 2008 summarises earlier research on this link, including the widely cited analysis by Claxton, Cramer and Pierce from 2001. That analysis looked at 76 studies with electronic monitoring of medicine intake and found an average adherence rate of 71 percent, ranging from 34 to 97 percent depending on the condition studied. The key finding: adherence was significantly higher with once-daily dosing than with dosing three or more times a day. Between once and twice daily, however, there was no measurable difference, nor between twice and three times daily.

These findings explain why complex schedules, for example five different medicines at three different times of day, some with and some without food, are particularly prone to mistakes and missed doses. Not because the people affected are careless, but because the simple mental load of remembering several separate times and combinations grows with each additional dose per day. As people get older, taking several medicines at once (polypharmacy) also becomes more common: treating several chronic conditions at the same time is the rule rather than the exception in later life.

Can design and packaging really help?

This is where a branch of research comes in that looks specifically at aids such as pill organizers, weekly boxes and specially designed blister packs. A widely noted meta-analysis by Vicki Conn and colleagues, published in 2015 in Current Medical Research and Opinion, combined 52 studies with a total of around 22,858 participants. The result: people who used a packaging or organisation aid reached an average adherence of 71 percent, compared with 63 percent in the control groups, a statistically significant if moderate difference.

An important point for context: the studies in this meta-analysis were very different, from simple daily dose boxes to electronic reminder packaging, and the effects varied accordingly. A single aid doesn't work equally well for every person and every condition, and the authors themselves point out the high variation among the included studies. Still, the finding shows a trend: better visibility and structure of intake can make a measurable difference, even if it is no guarantee.

Why visibility and looks matter at all

An obvious but often overlooked point: an aid only helps if it is actually used, and what gets used is more likely to be something that fits well into daily life, sits visibly in a fixed place and doesn't look like a medical device. Design research on everyday objects for older people has pointed out for years that clinical-looking objects end up in drawers more often than objects that visually fit into a home. This is not proof that looks alone improve adherence; controlled research that directly tests design variants against each other is missing. But it is a plausible reason why an aid stays on the shelf instead of disappearing into a drawer.

When safety itself becomes an obstacle

Another often overlooked aspect is not about memory but about simple handling: many medicine packs are child-resistant for good reason, but exactly these closures can become a hurdle of their own for people with limited fine motor skills, for example due to arthritis or rheumatism. A member survey by the Swedish Rheumatism Association among around 2,245 people found that 92 percent sometimes and 22 percent even daily have difficulty opening medicine packaging. The association itself points out that this was an open, non-representative member survey, so the figures should not be mistaken for a solid scientific prevalence. As a sign of a real everyday problem, they are still useful.

This tension between safety and accessibility has been known in packaging research for decades: a closure that reliably keeps children out must not be so easy to open that it fails its purpose, yet it should not lock out adults with limited strength or mobility. It is a trade-off with no perfect, universal solution, only new compromises between the two requirements.

The limits of the research, honestly considered

As clearly as the WHO's 50 percent figure is quoted, it remains unclear in research what really helps reliably. The best-known Cochrane review on the topic, last updated in 2014 by Robby Nieuwlaat and colleagues under the lead of Brian Haynes, analysed 182 randomised studies. The conclusion is deliberately cautious: only 17 of the included studies had a sufficiently low risk of bias, and even among these, only five improved both adherence and actual health outcomes. A statistical summary across all studies was not possible because of the large differences between them. The authors explicitly state that it remains unclear how adherence can be improved reliably and sustainably; even the most effective measures studied did not lead to large improvements.

This caution matters: neither reminder apps nor pill organizers nor counselling sessions are a magic solution. What works in individual studies cannot automatically be generalised, and the most successful approaches were often complex, multi-part programmes with personal support from pharmacists or nurses, not a single aid on its own. Anyone who reads that packaging or organisation "solves" the adherence problem is overstating the research. More realistic: good organisation and visibility are one building block among several, not a cure-all.

What this means for everyday life

A few sober conclusions for daily life can be drawn from this research without making promises. First: complexity is the biggest enemy of adherence, not a lack of will. Simplifying a medication schedule as far as possible, always together with the doctor or pharmacy and never on your own, measurably reduces the risk of mistakes. Second: visibility counts. An aid that disappears into a drawer naturally can't remind anyone. Third: routines are more stable than good intentions. Linking intake to a ritual that happens every day anyway, such as breakfast or brushing your teeth, is repeatedly described in habit research as more helpful than reminders alone.

In the end, a figure as plain-looking as "50 percent" has enormous practical significance: for health systems as much as for the individual kitchen table where the packs pile up.

Frequently asked questions

What exactly does the WHO's 50 percent figure measure?

It describes the average of how often people with chronic conditions in developed countries actually take their medicines as prescribed over a longer period. It is a rough mean across many conditions and studies; the actual values vary considerably depending on the condition.

Is forgetting the main cause of not taking medicines?

Forgetting, or unintentional non-adherence, is a big factor but not the only one. Deliberate decisions also play a role, for example because of side effects, doubts about whether the therapy is needed, or costs.

Do pill organizers demonstrably improve adherence?

A 2015 meta-analysis found a moderate, statistically significant difference in favour of packaging and organisation aids. However, the underlying studies were very different, and a single aid doesn't work equally well for all people and conditions.

Why does the number of doses per day matter?

Research shows that adherence is significantly higher with once-daily dosing than with three or more doses per day. Between once and twice daily, however, the underlying analysis found hardly any difference.

Is there a simple solution to the adherence problem?

No. The current Cochrane review on the topic comes to the honest conclusion that it is unclear how adherence can be improved reliably. Even the most effective measures studied led only to moderate improvements, usually through a combination of several approaches.

Does this mainly affect older people?

Not exclusively, but taking several medicines at once, meaning treating several chronic conditions at the same time, becomes much more common with age, which brings more complex schedules and therefore a higher risk of mistakes.

Looking ahead

For exactly these complex schedules spread across the day, Oxionix is developing a smart pill box, the Etui. According to current plans, it is meant to give people who take several medicines a clear, easy-to-follow structure for their intake, without looking like a clinical aid. It is a product in planning with no fixed delivery date; how it will actually affect daily life remains to be seen. More on the current plans in our journal article on the smart pill box Etui.

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