The comprehensive conceptual model of health literacy (see figure below) focuses on how people access, understand, appraise, and apply information concerning healthcare, disease prevention and health promotion. It explains how health literacy develops across the life span and illustrates the influence of personal, situational, and contextual factors, such as social and environmental determinants. The model also demonstrates how health literacy can impact health system use and costs, health behaviour and health outcomes, participation and empowerment, equity, and sustainability. While it is highly relevant for individuals and populations’ ability to act on health matters, health literacy also depends on the support provided by health systems, such as services being easy to access and navigate, clear communication, and informed decision-making. 

Figure: Health literacy conceptual model 

Health literacy is critical to efficient and trustworthy health systems. It enables people to continually learn new information and to ‘unlearn’ outdated information to maintain good health and act as informed users of health services. 
Developing the health literacy of both people and systems, and building the reciprocal responsibility between them, strengthens the equality of opportunities in accessing healthcare. Importantly, the vulnerability of people is determined and impacted by their competencies and needs, as well as the organisation of the health services. The development of health literacy should therefore be guaranteed to all, including people in vulnerable situations facing health literacy challenges.  
 

Health literacy is an important determinant of health and a constituent of avoidable and unfair health inequalities. A strong socio-economic gradient has been identified which indicates how low socio-economic status, low education, adverse health behaviours, poor self-reported health, and increased use of services correlates with limited levels of health literacy. Health literacy gaps can lead to inequities between countries and between different population groups within countries.

Poor health literacy is a drain on human and financial resources and an obstacle for sustainable development. The economic research on health literacy in Europe is scarce. Estimating the costs of poor health literacy is a complex area which requires some assumptions to be made. US research suggests that the annual cost of poor health literacy is 3–5% of the health budget[1]. Based on these estimates, the cost of poor health literacy in England could be £2.95–4.92bn (based on the NHS England budget for 2014-15 being £98.4bn)[2]. However, it is difficult to accurately transfer US cost implication findings to health systems in Europe. A recent study conducted in the US among Medicare beneficiaries estimated that improving health literacy could prevent nearly one million hospital visits and save over $25 billion a year[3]. 

Together with the European Convention on Human Rights and the European Social Charter, the Convention on human rights and biomedicine (Oviedo Convention) provides a human rights framework relevant in the field of health laying down principles which respect, and implementation may be substantially impacted by, health literacy.  For example, the principle of informed consent to undergo a health intervention (Article 5, Oviedo Convention) involves being able to access and understand appropriate information to consent to it. In other words, health literacy (understanding and access to information, critical thinking) enables individuals to assess the benefit and risks of an intervention so that fully informed decisions can be reached. 
Health literacy makes an important contribution to attaining goal 3 “Ensuring healthy lives and the promotion of well-being for all at all ages” of the United Nations Sustainable Development Goals. Health literacy can be considered a tool to empower people, using various forms of communication and action taken through health systems and other policies, to gain access, understand and use information in ways which promote and maintain good health. Furthermore, health literacy provides a strategic approach to achieving the highest attainable standard of health for everyone, based on four essential elements: 1) Availability: the need for public health and health care facilities, goods, and services, as well as programmes for all; 2) Accessibility: health facilities, goods and services must be accessible to everyone and exercise non-discrimination, be affordable, provide access to information and be within (physical) reach; 3) Acceptability: all health facilities, goods and services must be respectful of medical ethics and culturally appropriate; 4) Quality: health facilities, goods and services must also be scientifically and medically appropriate and of good quality, including engagement of skilled health care personnel. 
 

Health systems and their operators and providers are critically important in enabling people to make free and informed choices about their health. Health literacy empowers patients to face the complexities of these systems, to become familiar with their knowledge and methods, to enable them to assess information, and to decide on treatment and care.

Health literacy is important in the broader context of health prevention. It concerns the understanding of different scientific and clinical information to promote health outcomes (health prevention measures are taken to avoid illness and so they may not be personally experienced, unlike treatments and therapies which have a tangible effect on people during illness).

Consider the following examples:

• The Covid-19 pandemic prompted the largest vaccination campaign in human history. Among the many challenges faced by individuals was the assessment of risk vs benefit of vaccination (arguably requiring a deep conceptual comprehension of statistical data, such as percentage, probability, predictive models, and different scenarios). In this regard, health literacy can help people to perceive, understand and assess associated risks.
• Eating a healthy diet contributes to a healthy life, including lower risks of cardiovascular disease. Diet is strongly dependant on the cultural and geographical dimensions of people and groups in society. In this regard, health literacy contributes to the skills, sensibilities and empathy needed towards different people and groups in order to be more effective in encouraging changes in their daily diets.

Consequently, health literacy can be considered as a determinant of both personal and public health. It contributes to the health of individual persons and to the health of communities or other collectives of individuals with a shared health knowledge. In other words, health literacy is essentially a relational activity which can facilitate improvements in general well-being, including for people in vulnerable situations.