National measures of health literacy

Several surveys of U.S. adults show little improvement in health literacy of decades.

Over the past 24 years, there have been studies of adult literacy in the United States. The 1992 National Adult Literacy Survey (NALS), 2003 National Assessment of Adult Literacy (NAAL), and the 2012 Program for the International Assessment of Adult Competencies (PIAAC) show that adult literacy skills have changed relatively little over time. According to the PIAAC, only 12 percent of adults showed the highest proficiency level on literacy tasks, and even less, 9 percent, showed proficient skills in basic math. These results are the same as a decade earlier when the NAAL demonstrated that only 12 percent of adults had proficient health literacy skills. What is the connection between literacy and health? Adults with higher literacy scores report better health, which suggests they have a stronger set of skills to prevent disease and protect their health.

The NAAL was administered to more than 19,000 adults, aged 16 and over, in households or prisons. Unlike indirect measures of literacy which rely on self-reports and other subjective evaluations, this assessment measured literacy directly through tasks representing a range of activities adults are likely to face in their daily lives.

All of the activities required the ability to read and understand written and printed information. According to this survey, there are four levels of health literacy: below basic, basic, intermediate and proficient. Here is a summary of what was discovered:

Below Basic

Fourteen percent had below basic health literacy. At this level, abilities range from being non-literate in English to being able to locate straightforward information in short simple texts. For example, being able to identify what is permissible to drink before a medical test, from a set of short instructions.

Among adults who received Medicare and Medicaid, 27 percent and 30 percent respectively, had below basic health literacy. These individuals are more likely to report their health as poor (42 percent) and are more likely to lack health insurance (28 percent) than adults with proficient health literacy. Close to 30 million people in the U.S. have below basic health literacy.


Twenty-two percent of those surveyed had basic health literacy. At this level, abilities include finding information in texts somewhat longer and more complex than those below basic. For example, being able to give two reasons why a person with no symptoms should be tested for a disease, based on information provided in a pamphlet. 75 million U.S. adults have basic health literacy.


The majority of adults, 53 percent, had intermediate health literacy, with skills necessary to perform moderately challenging literacy activities. For example, people who fell into this category were able to determine a healthy weight range for a person of a specified height, based on a graph that relates height and weight to body mass index.


Twelve percent of U.S. adults were proficient in health literacy, a skill level necessary to perform more complex and challenging literacy activities. This includes reading lengthy, abstract documents, synthesizing information and making complex inferences. For example, calculating an employee’s share of health insurance costs using a table.

NAAL data from 2006 shows that limited health literacy disproportionately affects populations that are underserved and at risk for certain health problems. For example, adults who did not graduate from high school make up 51 percent of those in the “below basic” category. This represents 15 percent of the total population.

Individuals with one or more disabilities comprise 48 percent of the “below basic” category. They represent 30 percent of the total population. Those who did not speak English before starting school make up 39 percent of adults whose health literacy is “below basic.” They comprise 13 percent of the total population.

The responsibility for improving health literacy lies with many of us. Public health professionals and the healthcare and public health systems play a big role. Michigan State University Extension is working with partners to ensure that health information and services can be understood and used by all Americans. 

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