Aim To identify diabetes nurses' experience with patients' three hierarchical levels of health literacy (HL): Functional HL (FHL), interactive HL (IHL) and critical HL (CHL). Background Diabetic patients receive health information from many sources of varying quality, while individual responsibility for their own health is emphasized. This requires that patients can evaluate the quality of health information. Such skills reflect health literacy (HL), which focuses on understanding, gaining access to, critical evaluation and use of health information for the acquisition of good health. Method A questionnaire, mainly consisting of 5-point Likert-scaled attitude statements reflecting FHL, IHL and CHL, was developed. A total of 108 diabetes nurses responded (40% response rate). Through factor and reliability analysis, FHL, IHL and CHL constructs of the statements were established. Results The FHL, IHL and CHL constructs were consistent with HL-theory. Some construct statements achieved low mean scores. The mean score on CHL construct was lower than the corresponding scores on the FHL and IHL constructs. Conclusion Diabetes patient's HL should preferably be explored. Since the patients might have varying degrees of HL, diabetes nurses should take this into account during health communication between them and the patients.