This study is the first to place HL, SE, PE, and SCB in patients with type 2 diabetes in the same model to explore their pathways used PLS-SEM, and their differences in terms of the patient preference for decision-making.
These findings clarify the relationships of HL, SE, and PE to SCB, which are: HL directly positively influences SE and SCB, and SE directly positively influences SCB. HL can also indirectly influence SCB through SE. These relationships were consistent with previous researches [7, 16, 17]. Patients with higher HL can better promote their own health-related behaviors, and they may feel more confident in their ability to complete SCB [41, 42]. In particular, IHL and CHL have a greater impact on SE than FHL . The more patients can enhance their SE, the more they may feel empowered to handle their situation , so HL plays an important role in the impact of SCB, and SE is also an important predictor of SCB .
This study also further clarified the effect of HL and PE on SCB, which is: HL directly positively influences PE, and PE directly positively influences SCB. HL can also indirectly influence SCB through PE. Studies have shown that HL and PE are deeply interwoven , and each independently affects SCB , but limited HL is a threat to PE and self-management . Wang et al.  proposed that PE may promote SCB in patients with high IHL and CHL, but may have no effect on SCB in patients with low communicative and critical health literacy (CCHL). Obviously, no matter patients are empowered externally or internally, these empowerment may sustained only when patients have adequate HL. Increasing HL is an antecedent of PE [46–48]. Strengthening PE without adequate HL may lead patients to harm their health condition by making uninformed decisions, and HL plays a bigger role than PE in determining health status .
In this study, the mean PE was 4.03 and the mean SE was 3.82, indicating that patients tended to have more PE than SE. The combined care plans for patients with type 2 diabetes under the National Health Insurance System in Taiwan encourages patients to be empowered by health providers, so PE and SE are generally high. However, the mean of the HL scale was 3.42, indicating that patients’ HL was obviously insufficient, and the mean of the SCB scale (3.66) was not high as well. Although these patients had the beliefs and actions to perform health behaviors and wanted to control their own health behaviors, they still felt a strong sense of powerlessness. Therefore, the self-management behaviors of the patients relied too heavily on the health care system to take active responsibility for SCB. The mindset of these patients must be changed, and their self-improvement in HL is the cornerstone by which to promote SCB.
In terms of the differences in preference in decision-making (SDM vs physician decision), HL directly positively affected SE in the five paths of Fig. 1 significantly more for the SDM group than for the physician decision group. Because HL can improve the ability of the patient to perform SCB, the patient then is better able to participate in SDM , further influencing clinical decisions. Patients will be more confident to take on self-management when they have more health-related knowledge, feel they can seek out resources and applications, and have positive interactions with health care professionals. As a result, the self-efficacy of patients is also improved. The study by Brabers et al.  showed that HL was associated with patient involvement in SDM, especially CHL. Patients participating in SDM have an increased commitment to health behaviors  and greater awareness and confidence to start their treatment . Also, because patients with HL are more likely to play an active role in clinical decision-making, patients with HL are much more likely to show behavioral change . Because HL involves all aspects of health care, such as prevention, screening, diagnosis, and treatment, it is considered the basis of the health care delivery system .
Limitations of this study include the fact that participant inclusion was based on patient consent, which may have introduced selection bias into the study sample. This study sample of a single regional hospital may not be generalizable. Also, the sample included only outpatients with type 2 diabetes; those with other types of diabetes or more advanced disease may have different outcomes. Further study is needed to explore the specific factors that influence HL, in order to develop an effective promotion strategy and the associated application tools. Overall, improving the HL of patients with diabetes can enhance their self-care ability.