Physicians may assume patients can interpret prescription drug label instructions, yet four out of five patients (79%) in this study misinterpreted one or more of the ten common prescription label instructions they encountered. Although the instructions were brief and of minimal reading difficulty, rates of patient understanding varied widely across all literacy levels. More explicit language instructing patients when to take the medicine using time periods were better understood compared to instructions that more vaguely stated the number of times per day or hourly intervals. This finding is supported by prior research demonstrating that older adults have greater difficulty interpreting medication instructions that do not explicitly detail how and when to take a prescribed medicine13–15
Labels that instruct patients to take medications “twice daily” or “every 12 hours” require patients to make additional mental steps to infer when to take a medicine. For patients with limited literacy, this adds an unnecessary cognitive burden, resulting in poorer comprehension12
. Despite the use of more precise instructions, however, comprehension among those with low literacy skills was still significantly lower than patients with marginal or adequate literacy skills. This is also not surprising, as earlier health literacy studies found that materials with low reading grade levels were likely to improve comprehension among patients with adequate literacy, but had only variable success in improving comprehension among patients with low literacy22
Interestingly, identifying specific times each day (8 A.M., 5 P.M.) for administration was a more easily understood instruction format than stating times per day or hourly intervals. However, patients were significantly more likely to misinterpret these instructions compared to those stating time periods in the day (morning, evening). It is possible that patients do not need such precision when following medication instructions. Stating frequency using time periods of day rather than precise times may better reflect patients’ preference to tailor the implementation of their drug regimens to their daily schedule. Also of note, more complex dose regimens requiring patients to take more pills a day was a significant independent predictor of misinterpretation of instructions. A prescription requiring a patient to take four pills a day was 47% more likely to be misinterpreted than instructions for a ‘one-a-day’ regimen. Patients with low literacy did not differ significantly from those with adequate literacy in interpreting instructions to take one pill a day, or even understanding “Take 2 pills by mouth every day” and “Take 1 with breakfast and 1 with supper.” Although the latter instruction involved taking pills two times daily, the label broke down the instructions for dose and frequency and provided a context for the time of day.
The limitations to our study should be noted. First, we investigated patient understanding of different styles of writing instructions included on the primary label for prescription medications only. The association between misunderstanding of these instructions and medication error was not examined. We also did not study patients’ actual prescription drug-taking behaviors. Patients’ motivation, concentration and comprehension might have been greater if they were reporting on their own medicine given by their physician for conditions they or their children actually had14,23,24
. Second, since the study design did not include a chart review, we did not have information on patients’ health information; in particular whether they had actual experience with the study medications. Third, we primarily manipulated the language for frequency of use; however there were more subtle differences in word choice and numeric presentation of dose on the various drug instructions that may also have altered patients’ understanding. Fourth, patients in our study were mostly socioeconomically disadvantaged individuals from three primary care clinics in diverse areas of the country. Our sample addresses those individuals disproportionately affected by poor health outcomes, and whose health care are targeted for improvement by Healthy People 201025
. Finally, the generalizability of our findings are further limited by the fact that patients were predominantly female (an accurate depiction of the clinic patient populations), and that participation was limited to patients who spoke English. This was due in part to criteria for using the Rapid Estimate of Adult Literacy in Medicine (REALM) as our literacy assessment.
While further improvements might be made in the design of prescription drug labels, it is likely that patient counseling will also be needed to address health literacy deficits. Previous research has found physicians do not commonly review the instructions when prescribing medications, nor do pharmacists routinely verbally counsel patients when filling a prescription26–29
. Both the American Medical Association and American Pharmacists Association recommend provider training in health literacy communication ‘best practices’29,30
. A highly efficacious approach described in recent cognitive factors research, known as “implementation intention” might also aid provider training activities31
. This could be a promising health literacy strategy at the provider level, as it refers to a process of helping patients visualize exactly how a prescribed medication will be self-administered within the context of their own daily routine. As minimal standards exist to guide physician and pharmacist best practices for writing and transcribing the dose and frequency of use on label instructions for patients, both professionals should make it their goal to be simple, clear and explicit in directing patients on how to self-administer their medication.