Background <p>Health literacy is an important determinant of health-related behaviours, self-care, and health outcomes, but large-scale evidence on self-perceived health literacy remains limited, particularly in Central and Eastern Europe. This study examined the association between self-perceived health literacy, health behaviours, self-rated health, and selected health indicators in a large sample of adult Polish internet users. Self-perceived health literacy was assessed using a single self-assessment item from the 2024 National Health Test of Poles (NTZP).</p> Methods <p>This cross-sectional secondary analysis used an anonymised dataset of 120,000 adult respondents from NTZP 2024, a nationwide CAWI survey. The analytical sample was weighted by sex, age, educational attainment, and size of place of residence to reflect the structure of Polish internet users aged 18 years and older. Self-perceived health literacy was analysed primarily as an ordinal variable to preserve the ordered structure of the response scale. Associations with sociodemographic characteristics, health behaviours, self-rated physical and mental health, chronic conditions, and selected health complaints were examined using correlation analyses and regression models appropriate to the scale of the variables. For selected binary outcomes retained for descriptive comparability, effect estimates were reported as odds ratios (ORs) with 95% confidence intervals.</p> Results <p>Higher self-perceived health literacy was consistently associated with more favourable health-related profiles. Respondents with higher self-perceived health literacy were more likely to report regular physical activity (OR = 1.66) and daily vegetable consumption (OR = 1.83), and were more likely to report very good physical health (OR = 2.50) and very good mental health (OR = 2.20). Higher self-perceived health literacy was also associated with lower frequencies of selected symptoms, including insomnia (OR = 0.60), chest pain (OR = 0.43), memory problems (OR = 0.50), and work-related exhaustion (OR = 0.59). Correlation analyses showed that the strongest positive associations were observed for education, physical health, and mental health.</p> Conclusions <p>In this large cross-sectional study, higher self-perceived health literacy was associated with better self-rated health, more favourable health behaviours, and a lower burden of selected somatic and mental health complaints. These findings support the relevance of self-perceived health literacy as a population health correlate and as a potentially useful consideration in public health planning. Because of the cross-sectional design and the use of a survey-specific self-report measure, the findings should be interpreted cautiously and not as evidence of causal effects.</p>