The concept of health literacy has gained the attention of the health researcher world. Simonds (1974) introduced this idea to the nursing literature the first time. The past research documented a few references related to health literacy by 1992. Health literacy originates from the field of public health, where it advanced in health education, protection, promotion, and primary health prevention . As a result, healthy literacy is a relatively innovative concept for the health staff, including nurses, with few references associated with health literacy, which appear in nursing and health education literature [36, 37]. In recent times, patients have to encounter the difficulties of complex healthcare systems. Patients have to acquire sufficient knowledge to understand the multifaceted information and find solutions to the complex health care systems. Accordingly, it is vital to evaluate health literacy among diabetes patients and provide them easy-to-understand and required support information associated with health literacy level. Hence, assessing patients’ health literacy is critical to provide the necessary support to diabetes patients, as diabetes needs expensive medical treatment and self-care. It is essential that diabetes patients’ understand health information, such as symptoms and signs of their diseases. Patients require to know how to control and manage the disease . This study focused on investigating the influential factors that affect the health literacy status of patients’ with type-2 diabetes through demographic variables.
This study survey revealed that the average level of health literacy of diabetes patients with type 2 indicated 2.70 ± 0.44. The findings specified a favorable condition. Researchers conducted national research surveys, and studies reported 56% of the health literacy level among Iranian people, which is a limited or inappropriate level of the public health status. The findings of this study are in line with the previous national-level studies. This study revealed that mean scores of the patients’ demographic variables and health literacy are better than the findings of the earlier studies in Iran. However, the study place, patients' age, gender, residential locations, and sample size of the population are helpful to describe the difference of the study findings . The results of the current study are almost equal to the average level of health literacy of diabetic patients with the studies done by Reisi et al. , Tahery et al. , Rafiezadeh et al. , Yeh et al. , Reisi et al.  and patients with severe kidney problems in Japan . This finding is consistent with the results of a study done by Maleki et al. . On the other hand, Tehrani Banihashemi et al.  and Reisi’s et al.  studies have finally reported the level of health literacy in Iran, which is not consistent with the findings of the current study.
Likewise, the results of this study revealed that the field of health literacy, the subjects performed poor performance. Therefore, the lowest score of health literacy in diabetic patients related to this field of health literacy and on the other hand the highest average rating in the health literacy field is related to critical health included numeracy skills (ability to use quantitative information) and using this information to make further decisions. The results of the study Reisi et al. , Lai et al.  received the lowest score in terms of performance. In the van der Vaart’s study , patients with rheumatoid arthritis received the highest score in terms of performance. Since the above study was conducted in the Netherlands, where the literacy rate and reading and writing skills are 96.5% , thus, compared to the current study, the high level of functional health literacy in the studied people seems reasonable, which was inconsistent with the results of the present study.
Scholars argued that skills related to operational, communicative, and critical health literacy are necessary. The essential factors for improving self-care in diabetic patients are vital because these skills increase patients' self-confidence to communicate efficiently with health service providers and improve the health and abilities of patients to participate and cooperate with the health care system. These capabilities eventually permit patients to receive and evaluate the information they need from different communication channels and finally apply it in practice. Critical health literacy is a prerequisite for achieving a correct understanding of the political and social factors and determinants that provide the environment for health promotion and healthy living. Because of the broader skills range related to functional, communicative, and critical health literacy, their direct association with self-care in diabetic patients is possible. These levels of health literacy, social and cognitive knowledge, provides skills, and necessary understanding is for proper management of the disease by patients .
A study reported that diabetes patients with a higher level of critical and communicative health literacy skills actively applied required information to manage the situations, and they achieved accomplishments successfully. Thereby, better health literacy skills are useful in attaining improved self-efficacy . Ishikawa and Yano conducted a study, explained that diabetes patients with a better health literacy level would end to describe a better participation level, and enhanced self-efficacy to control diabetes disease .
The results revealed that there was a significant relationship between gender and health literacy of type 2 diabetic patients; these results are consistent with the study of Yeh et al. . Though, the results were inconsistent with the results of the studies done by Pooryaghob et al. , Charoghchian Khorasani et al.  Noroozi et al.  and Von et al. . The results of the study done by Maleki et al.  and Le et al.  Khosravi et al. , Tahery et al.  disclosed that there was a significant relationship between gender and health literacy and men's health literacy was higher than women, which is consistent with the current study. It could be due to men's higher education than women's.
In the current study, there was no significant relationship between the average ages of people with health literacy in type 2 diabetic patients; these results are consistent with the review of Charoghchian Khorasani et al.  research. But, the results were inconsistent with the results of the studies done by Yeh et al. , Noroozi et al. , and Tahery et al. . As a result, when reading comprehension is a necessary skill for receiving information, age is a factor that should be considered. Hence, when providing information to diabetic patients, it should not be limited to print media, and other teaching methods such as lecturing and group discussion should be used, as older people may be less literate.
The results of the current study disclosed that there was no significant relationship between marital status and health literacy of diabetic patients. These results are consistent with the study of Ansari et al. , Mohammadi et al. , and Almigbal et al. . Nevertheless, it was inconsistent with the results of the study done by Alidosti et al. .
The results of the current study disclosed that there is a significant relationship between education and health literacy of diabetic patients. These results are consistent with the investigations of Yeh et al. , Rafiezadeh Gharrehtapeh et al. , Noroozi et al. , Sahrayi et al. , and Ansari et al. . Likewise, in other studies, education is an active factor in the level of health literacy [8, 23, 60, 61]. Izadirads et al. study, it has been reported that having higher education and functional job status has led to an increase in the level of health literacy . Patients with lower levels of education also have lower levels of health literacy and have difficulty understanding and applying health information, application and administration of drugs, and understanding medical prescriptions; so, they require specialized training and attention . However, it is vital to note that during clinical appointments, physicians need to regulate their communication according to the patient's actual health literacy. Some simple techniques for this purpose include the use of simple language, low speed, and the participation of prominent family members in discussions . In a study on a 10-year study of a cohort in the United States it was found that low levels of education were associated with reduced physical activity, and the higher the level of education, the greater the physical activity. Generally, it assumed that the higher the level of literacy of people, the higher their health awareness. Thus, the healthier their lifestyle and the lower the prevalence of type 2 diabetes.  it could result because of the group with higher education, which is more likely to have more senior health-seeking behavior. Critical thinking was leading to them obtaining more information on health and better health literacy.
The results of the current study indicated that there is a significant relationship between job and health literacy of diabetic patients. These results are consistent with the studies done by Getaye Tefera et al. , Rafiezadeh Gharrehtapeh et al. , Noroozi et al. , Khosravi et al.  and Izadirad et al. . Nonetheless, the results were not consistent with the results of the study conducted by Kooshyar et al. .
The results of the current study revealed that there is a significant relationship between monthly income and health literacy of diabetic patients, which is consistent with the results of studies done by Tefera Getaye et al. , Charoghchian Khorasani et al. , Reisi et al. , and Ansari et al. . This result was inconsistent with the results of the study conducted by Mashi et al. .
The results of the current study disclosed that there was no significant relationship between the accommodation and health literacy of diabetic patients. These results are consistent with the results of studies done by Tefera Getaye et al. , Noroozi et al. , and Tehrani Banihashemi et al. .
The results of the present study revealed that there was no significant relationship between the type of treatment and health literacy for diabetic patients. These results are consistent with the studies done by Noroozi et al. , and Seyedoshohadaee et al. . The results of Osborn et al.'s study  presented a significant relationship between health literacy scores and drug compliance. The results of Mancuso and Rincon's study in diabetic patients indicated a low rate of adherence to diet and medication in diabetic patients. However, the rate of adherence to diet and medication in diabetic patients reported 36–54% in Rubin and Richard's studies . In the study of Osborn et al. , there was a statistically direct and significant relationship between health literacy scores and adherence to drugs among diabetic patients, which is not consistent with the results of the present study. In another study by Noureldin et al., it was found that patients with health literacy with adequate heart failure had better adherence to diets than those with inadequate health literacy. Also, health literacy could be an essential factor in sustainable drug interventions. So that in different studies, diverse responses have been designed to improve the level of health literacy in patients and have achieved positive results based on the effectiveness of interventions to improve health literacy in following patients' drug therapies . In their study, Raehl et al. showed that the health literacy level of elderly patients is significantly related to their adherence to their medication regimen . At large, patients with a higher level of education are more aware of the disease complications, self-care, and how to take medication and follow a diet. They have more access to educational resources .
The results of the current study disclosed that there was no significant relationship between the mean duration of diabetes and the health literacy of diabetic patients. In this regard, studies by Noroozi et al. , Maliki et al.  and Souza et al.  also suggested that health literacy was not associated with the duration of the disease. It expected that as the duration of the disease progresses, the level of the patient’s health literacy and their experiences will increase. Therefore, in order to increase the level of health literacy of patients, it is necessary to take steps to promote the provision of educational classes and the use of simple educational tools, understandable and straightforward expressions for patients, especially those with lower education and higher age.
The results of the current study indicated that there was no significant relationship between family history and health literacy of diabetic patients. These results are consistent with the study of Teferaet Getaye et al.  and, are not compatible with the research of Tol et al. , this may be due to a lack of sensitivity and a lack of attention to the consequences of the illness.
The results of the present study disclosed that there was no significant relationship between diabetes complications and the health literacy of diabetic patients. So, it was not possible to compare the findings with the previous results. Accordingly, it was not possible to compare the findings with the earlier results.
The results of the current study indicated that there was no significant relationship between abdominal obesity and the health literacy of diabetic patients. In the study of Afkhami et al. , it was reported that abdominal obesity was widespread in patients with type 2 diabetes, which is similar to the present study.
In this study, no significant correlation was observed between health literacy and smoking in patients with diabetes. These results are consistent with the research done by Mohammadpour et al. . In Friis et al.'s study, the correlation between health literacy and self-care behaviors in diabetic patients was examined, and it was found that there was no significant correlation between health literacy, tobacco use, and alcohol, which was consistent with the current study.
Based on multiple regression tests, in this study, among the demographic variables with the health literacy of diabetic patients, it was shown that among the imported variables, income, age, and employment variables remained as predictive variables in the final model. Accordingly, it was not possible to compare the findings with the previous results. Consequently, it was not possible to compare the findings with the previous results.
At present, treatment and diabetes management is challenging and complex. It requires special attention and the skills of health literacy associated with reading, arithmetic, and comprehension to control diabetes disease. These skills of health literacy are critical tools to help diabetes patients make appropriate and timely health decisions. Many factors may affect HL, such as age, school enrollment, race, socioeconomic status, and psychological distress. Several factors affect individuals’ health literacy, including age, gender, education, ethnicity, residential location, psychological distress, and socioeconomic status.
Limitation of the study
The scientific studies end up with some restrictions. This research survey reported some limitations, which are helpful for future investigations. The sample of this study used a convenience sample based on diabetes patients selected from targeted health centers. Therefore, the study findings are limited to this sample, and the results are not generalizable to other medical respondents' settings. Another limitation involved in this research survey reported the difficulty in instruments answering. The diabetes illiterate participants encountered problems filling the survey forms, and the investigators had to read the scale-items to the patients and record their answers accordingly. Besides, many literate diabetes patients faced difficulty with completing the inventory items because of their weak eyesight caused by diabetes disease. Further studies with specific geographic regions in various cultures can enrich the generalizability of the results. The results derived from this statistical sample suggest designing more studies on the area of health promotion with multiple factors, which would implement the results of this study on diabetes patients.